Office Error 0-1018: Fix Another Installation in Progress

Error 0-1018(0) — "Couldn't start Office installation. Another installation is in progress" — means the Office installer found a setup task it believes is still running, even when you can't see one. The fix, nine times out of ten: press Ctrl + Shift + Esc to open Task Manager, go to Details, end OfficeClickToRun.exe and OfficeC2RClient.exe, then run the Office setup again. If it still refuses, restart the PC properly and, in the stubborn cases, remove Office completely with Microsoft's Get Help uninstall tool and reinstall it fresh. Every route is below, sorted by symptom.

The Saturday this error cost Jake a sale

Jake runs a small mobile phone and computer shop. Saturday afternoon, a customer buys a laptop and a Microsoft 365 Family subscription on top — a nice clean sale. Jake offers to set it all up at the counter. Windows signs in, the Microsoft 365 download starts, and then the screen he'd never seen before: "Couldn't start Office installation. Another installation is in progress. Please try installing Office again after it's finished. Error code: 0-1018(0)."

Jake checked the taskbar. Nothing was installing. He tried again. Same error. Tried a third time while the customer looked at her watch. She left with the laptop, said she'd "sort the Office thing at home", and Jake spent the evening wondering whether she'd ask for a refund on the subscription instead.

He called Ethan that night.

Ethan: "The error is telling you the truth, just badly. Something was installing. You couldn't see it because the Office installer doesn't live on the taskbar — it lives in the background. Ten seconds in Task Manager and she'd have walked out with Word running."

Jake: "Then why does it say another installation? There was only one. Mine."

Ethan: "Because on a brand-new laptop, yours usually isn't the only one. That machine almost certainly shipped with a preloaded Office trial, and Windows Update was probably busy too, first boot out of the box. Three installers, one door. Only one gets through at a time."

That's this whole error in one line: one door, one installer at a time. Everything below is about finding out who's blocking the door, and moving them.

What error 0-1018(0) actually means

Modern Office — Microsoft 365, and the one-time-purchase Office 2016 through 2024 — installs through a Microsoft technology called Click-to-Run. Ethan's analogy for Jake: the old way of installing Office was like shipping a DVD — everything arrives, then it installs. Click-to-Run is like streaming a movie — Office starts working while the rest is still downloading in the background. It's why you can open Word two minutes into a Microsoft 365 install.

The part that matters for this error: Click-to-Run is built to run exactly one installation task at a time. Before it starts your install, it checks whether anything else is mid-flight. If the answer is yes — or if a leftover flag from a previous, broken install says yes — you get 0-1018(0). The "(0)" on the end is just a sub-code; for this error it carries no extra meaning worth chasing.

Four things trip that check in the real world:

• A hidden Office process is genuinely running. OfficeClickToRun.exe (the install/update engine) or OfficeC2RClient.exe (the client that talks to it) is doing something — often auto-updating an existing Office product you forgot was there.
• Windows Installer is busy. msiexec.exe is the installer used by thousands of other programs. If some other setup — a driver package, an update, another app — is mid-install, Office setup can refuse to start on top of it.
• Windows Update is in the middle of something. Common on brand-new PCs and freshly reinstalled ones: first boot, Windows Update grabs everything at once, and the Office installer walks into the traffic jam.
• A previous Office install died and left its state behind. Setup crashed, the PC lost power, someone cancelled it, or a preloaded trial was half-removed. The leftover state permanently answers "is an install running?" with yes. This is the case that survives restarts.

Jake: "So the error isn't lying. It's just counting installers I can't see."

Ethan: "Exactly. Which means the whole fix is: make the count zero. Kill the hidden process, wait out the genuine install, or wipe the corpse of the dead one. Which route you take depends on your symptom."

Which of these is you? Match the symptom first

Don't run every fix. Match your situation to a row and jump straight to that route — the routes are ordered from the twenty-second fix to the twenty-minute one, so if your row points at Route 5, you've saved yourself four fixes that were never going to work.

Route 1: End the hidden installer in Task Manager

This is the fix that clears most 0-1018 errors, and it takes under a minute. Task Manager is the Windows tool that shows every running process — including the invisible ones the taskbar never shows.

Step by step (same on Windows 11 and Windows 10)

1. Open Task Manager: press Ctrl + Shift + Esc. Or right-click the Start button and choose Task Manager — that works on both systems.
2. Open the Details view. On Windows 11, Task Manager has a menu down the left edge — click the icon that looks like three lines (top-left) if it's collapsed, then choose Details. On Windows 10, Details is a tab along the top; if you see almost nothing, click More details at the bottom-left first — Windows 10 ships Task Manager in a cut-down mode.
3. Find the Office installer processes. The Details list is alphabetical. Look for OfficeClickToRun.exe and OfficeC2RClient.exe. On Windows 11 you can just type "office" into the search box at the top of Task Manager — Windows 10's version has no search, so scroll to the letter O.
4. End them: right-click OfficeClickToRun.exe → End task. Confirm if asked. Repeat for OfficeC2RClient.exe and for any process starting with "Microsoft Office" or "setup" that mentions Office.
5. Check msiexec.exe too. If you see one or more msiexec.exe entries, that's Windows Installer working on something (Office or not). If it's been sitting there a long while and nothing visible is installing, end those as well.
6. Run the Office setup again — double-click the same OfficeSetup.exe you downloaded, or restart the install from office.com. It should now go straight into downloading.

Jake: "Hang on — I'm ending a thing called OfficeClickToRun while trying to install Office. Aren't I shooting the installer I need?"

Ethan: "You're shooting the stuck copy of it. When you relaunch setup, Windows starts a fresh one. It's the same as closing a frozen browser tab and opening a new one — you don't lose the browser."

If End task is greyed out or says Access denied

Windows sometimes protects installer processes from a normal user account. Close Task Manager and reopen it as administrator: press Win + S, type task manager, right-click the result and choose Run as administrator. If a process still refuses to die, don't fight it — go to Route 2 and stop the service that owns it instead. Killing the engine beats wrestling the wheel.

One genuine caution before you end anything: if the Office update window is visibly open and moving — a progress bar actually advancing — the kindest fix is to let it finish. Ending a live, healthy update mid-write is how you graduate from a twenty-second problem to a Route 5 problem. End tasks when things are stuck, not when they're merely slow.

Route 2: Restart the Click-to-Run service

Behind the process you just ended sits a Windows service — a background program that Windows itself starts and supervises, with no window of its own. Office's is called the Microsoft Office Click-to-Run Service. If ending the process didn't clear the error, restarting the service resets Click-to-Run's state more thoroughly.

Using the Services console (both Windows versions)

1. Press Win + R to open the Run box — the little "type a command" window Windows has had for decades. Type services.msc and press Enter. (An .msc file is a saved management console — a ready-made admin panel. This one lists every service on the machine.)
2. Scroll to Microsoft Office Click-to-Run Service. The list is alphabetical — it's under M, not O.
3. Right-click it → Restart. If Restart is greyed out, choose Stop, wait for it to stop, then Start.
4. While you're in there, glance at Windows Installer further down the list. Its status column is usually blank (it runs on demand). If it says Running and has been for a long time with nothing visibly installing, restart it the same way.
5. Close the window and run Office setup again.

The thirty-second version, for the terminal-comfortable

Right-click Start → Terminal (Admin) on Windows 11, or Windows PowerShell (Admin) on Windows 10, then run these two lines. They kill the stuck installer processes and bounce the service in one go — the same thing the clicks above do:

taskkill /f /im OfficeClickToRun.exe /im OfficeC2RClient.exe
net stop ClickToRunSvc && net start ClickToRunSvc

If the first command answers "process not found", that's fine — it means nothing was stuck, and your blocker is elsewhere. If net stop hangs for more than a minute, close the window, restart the PC, and pick up at Route 3.

Route 3: The Windows Update collision, and restarting properly

On a new or freshly reset PC, the most common blocker isn't Office at all — it's Windows Update installing a queue of patches on first boot. Office setup and Windows Update can collide over the same installation machinery, and a half-applied update that's waiting for a restart leaves the system flagged as mid-installation.

1. Open Settings (Win + I) → Windows Update. On Windows 10 it's Settings → Update & Security → Windows Update.
2. If updates are downloading or installing, let them finish. Fighting them wastes more time than waiting.
3. If it says Restart required — restart now, from that button.
4. When the PC comes back, run Office setup first, before opening other apps. You want the door to yourself.

Why "turn it off and on" sometimes doesn't work here

Here's the trap almost nobody mentions: on Windows 10 and 11, Shut down is not a full reboot. A feature called Fast Startup saves part of the system's state to disk at shutdown and resurrects it at power-on, to boot faster. Which means a stuck installer flag can survive a shut-down-and-power-on cycle — you think you rebooted, Windows knows you didn't. Restart, from the Start menu power button, is always a true full reboot. If you've been "restarting" by holding the power button or using Shut down, do one honest Restart before deciding this fix failed.

Route 4: The new-PC trap — the preloaded Office trial

This was Jake's customer's laptop. Most consumer laptops ship with Microsoft 365 preinstalled as a trial. On first boot it can wake up and start configuring or updating itself — and if you try to install your own Microsoft 365 at that moment, you collide with it. Worse, the preload sometimes sits half-configured and blocks installs indefinitely.

The clean sequence for any new PC:

1. Check what's already there: Settings → Apps → Installed apps (Windows 11) or Apps & features (Windows 10). Search the list for "Microsoft 365" or "Office".
2. If a preloaded copy exists, sign into it instead of reinstalling. Open Word, sign in with the Microsoft account that holds your subscription, and it activates. No second install needed — this is the step that would have saved Jake's Saturday. The preinstalled Office and "your" Office are the same software; only the licence differs.
3. If it's a trial you don't want (say, you bought Office 2024 outright instead), uninstall the preload first: select it in the apps list → Uninstall. Restart, then install yours.
4. If uninstalling the preload fails or the error persists afterwards, the preload was broken — go to Route 5 and remove it properly.

If Office asks you to sign in during any of this and throws a connection error instead of the 0-1018 screen, that's a different fault with a different fix — we cover it in fixing the "Sorry, we couldn't connect to Microsoft services" error.

Route 5: Full removal and clean reinstall — and where our 2016 advice went wrong

If the error survives Routes 1–3, some previous Office installation has left corrupted state behind — registry entries, scheduled tasks, Click-to-Run folders — and the only reliable cure is to remove every trace and start clean. This is exactly the case we hit in testing: a machine with a half-removed Office 2019 threw 0-1018 on every install attempt, through every restart, until the removal tool cleaned it out.

First, an honest correction of our own article

This post originally went up in April 2016, and its fix was to download Microsoft's O15CTRRemove.diagcab troubleshooter and let it repair the installation. That was the right advice then — it's how we actually fixed it that year. It is wrong advice now, and if you've arrived here from an old bookmark, here's what changed: .diagcab troubleshooters ran on a Windows component called MSDT (Microsoft Support Diagnostic Tool), which Microsoft deprecated and has since removed from current Windows 11 — on a 25H2 machine the old file simply won't open. Its successor, the Support and Recovery Assistant (SaRA) app, was itself retired in March 2026 and folded into the Get Help app built into Windows. Any site still telling you to download a .diagcab file — and plenty of copy-paste fix sites do — is recycling advice that stopped working, from sources you shouldn't trust with an installer file anyway.

The current removal procedure (Windows 11 and 10)

1. Normal uninstall first. Settings → Apps → Installed apps (Windows 10: Apps & features) → find every Microsoft 365 / Office entry → Uninstall. On Windows 11 the Uninstall option hides behind the three-dot menu on the right of each entry — one of those small UI moves that trips up Windows 10 upgraders.
2. Run the official cleanup. Open a browser and go to aka.ms/SaRA-officeUninstallFromPC — a Microsoft shortlink that launches the Get Help app with the Office uninstall assistant loaded. Choose Yes when it asks to run the troubleshooter, select the Office products it finds, and let it sweep. This is the step that removes what the normal uninstall leaves behind: stale Click-to-Run state, scheduled tasks, registry leftovers — the actual cause of a recurring 0-1018.
3. Restart the PC. A real Restart, per Route 3.
4. Reinstall from the source, not an old download. Sign in at account.microsoft.com → Services & subscriptions (or office.com → Install apps) and download a fresh OfficeSetup.exe. Run it. On a cleaned machine it installs without complaint — the door is finally empty.

The hard cases: when 0-1018 is telling you something else

You triggered it yourself: Visio, Project, or a second Office product

If you started installing Visio, Project, or a language accessory pack while Microsoft 365 was still installing, 0-1018 isn't a fault — it's the queue working as designed. Click-to-Run installs one product at a time, full stop. Wait for the first install to finish (check Task Manager if you're unsure whether it's still going), then run the second. Related rule while we're here: all Click-to-Run products on one PC must be the same architecture — you can't add 32-bit Visio to 64-bit Microsoft 365. If your second product's installer refuses with an architecture message, that's why.

The error returns after every restart

A restart kills processes, so if 0-1018 outlives reboots, a persistent thing is re-creating the blocked state: either the corrupted install state from a dead setup (Route 5 territory), or the Office Automatic Updates scheduled task firing at each boot and resuming a broken update. You can see the latter in Task Scheduler (Win + R, taskschd.msc, then Task Scheduler Library → Microsoft → Office), but don't bother disabling tasks by hand — the Route 5 removal deletes and rebuilds them, which is both easier and safer than surgery.

A work or school PC: you may not be allowed to fix this

Honest limit: if the machine belongs to a company or school and Office is deployed by the IT department (through Intune or similar), local fixes can be overridden by management policy — and running removal tools on a managed install can put you at odds with IT. The right move there isn't any route on this page; it's telling the admin the error code. This page is for machines you own.

Still on Windows 10? Here's the honest position

Everything above works identically on Windows 10 22H2 — we tested it there. But know where you stand: Windows 10's free support ended on 14 October 2025. Enrolling in Microsoft's consumer ESU program (free with settings sync, or a small one-time fee) keeps security updates coming until October 2027, and Microsoft 365 Apps themselves keep receiving security updates on Windows 10 until October 2028 — so Office isn't abandoning the OS overnight. Ethan's advice to Jake for shop customers on older machines: enrol ESU today, and use the breathing room to plan the move — whether that's a Windows 11 upgrade on eligible hardware or a new machine when the budget allows. An unpatched internet-connected Windows is not a plan.

Frequently asked questions

What does Office error code 0-1018(0) actually mean?

It means the Office Click-to-Run installer detected another installation task in progress and refused to start a second one. The blocking task is usually an invisible background process (OfficeClickToRun.exe or OfficeC2RClient.exe), a stuck Windows Installer job, a Windows Update running at the same time, or the leftover state of an earlier Office install that never finished. The "(0)" sub-code adds nothing useful for troubleshooting.

Why does Office say another installation is in progress when nothing is running?

Because the blocking task has no window. Click-to-Run works as a background service, Windows Installer jobs run invisibly, and a previously failed install can leave a flag that permanently claims a setup is mid-flight. Task Manager's Details view shows what the taskbar doesn't — which is why Route 1 starts there.

Is it safe to end OfficeClickToRun.exe in Task Manager?

Yes, when an install is stuck. It's the installer and update engine, not your documents or the Office apps themselves; ending it cancels the stuck task, and a fresh copy starts automatically the next time it's needed. The one time to hold off: a visibly progressing update window — let a healthy update finish rather than interrupting it mid-write.

Does the old O15CTRRemove.diagcab tool still work in 2026?

No — and this article once recommended it, so we'll be direct. The .diagcab format ran on MSDT, which Microsoft deprecated and removed from current Windows 11; the file won't open on a 25H2 machine. The SaRA app that replaced it was itself retired in March 2026. The current path is the Get Help app via aka.ms/SaRA-officeUninstallFromPC, as described in Route 5.

How do I completely remove Office before reinstalling?

Two passes. First the normal uninstall: Settings → Apps → Installed apps (Windows 10: Apps & features) → Uninstall every Office entry. Then the deep clean: run the Get Help uninstall assistant from aka.ms/SaRA-officeUninstallFromPC to remove leftover state, scheduled tasks and registry remnants. Restart, then reinstall fresh from office.com or account.microsoft.com.

Will uninstalling Office delete my documents?

No. Documents live in your Documents folder, desktop, or OneDrive — not inside the Office program files — and survive uninstall/reinstall untouched. If you use Outlook with POP email, note where your .pst data file lives before removing Office, purely for peace of mind; the uninstaller leaves data files alone as well.

Do I need to buy Office again to reinstall it?

No. Microsoft 365 is tied to your Microsoft account and reinstalls free on sign-in; a one-time Office 2021 or 2024 licence links to the account that first activated it. Sign in at account.microsoft.com → Services & subscriptions to redownload. The only people who "have to buy it again" are those who only ever had a preinstalled trial — that was never a purchase.

Can I install Office while Windows Update is running?

Best not to. The two can collide over the same installer machinery, and a pending restart from Windows Update is one of the classic triggers of this exact error. Let updates finish, take the restart, then run Office setup first thing after the reboot — the sequence in Route 3.

Why does error 0-1018 come back after every restart?

Because something persistent recreates the blocked state each boot — corrupted install state from a dead setup, or the Office Automatic Updates scheduled task resuming a broken job. Ending processes only treats the symptom. The cure for a recurring 0-1018 is the full removal and clean reinstall in Route 5; in our testing that was the only fix that held on a machine with a half-removed Office 2019.

Can I install Visio or Project while Microsoft 365 is installing?

No — Click-to-Run runs one installation at a time, so a simultaneous second install triggers 0-1018 by design. Let the first finish, then run the second. And all Click-to-Run products on the machine must share the same architecture: no 32-bit Visio alongside 64-bit Microsoft 365.

Does Office still work on Windows 10 now that support has ended?

Yes. Windows 10 hit end of support on 14 October 2025, but Microsoft 365 Apps keep getting security updates on Windows 10 until 10 October 2028, and the consumer ESU program patches Windows 10 itself until October 2027 for enrolled devices. Every fix on this page works on Windows 10 22H2 — just treat ESU enrolment as step zero if you haven't done it.

Is error 0-1018 the same as the 30015 and 30088 errors?

No. The 30015-x and 30088-x families mean the install started and broke — download or write failures, often disk space, antivirus interference or network trouble. 0-1018 means the install never started because another one was (or appeared to be) running. Route 5's clean removal fixes stubborn cases of both families, but check disk space and antivirus first for the 30000-series before doing anything drastic.

Worth reading next

Revision note. Originally published 13 April 2016, when the fix was Microsoft's O15CTRRemove.diagcab troubleshooter. Fully rewritten on 1 August 2026 to include Windows 11 25H2 (build 26200) and Windows 10 22H2 builds..