How to Fix Windows Update Error 0x80070020

By ErrorFix · Updated October 18, 2026 · 7 min read

What error 0x80070020 means

Under the hood, 0x80070020 is the system error ERROR_SHARING_VIOLATION — Windows-speak for "the process cannot access the file because it is being used by another process." When Windows Update downloads and stages its files, it expects exclusive access to them. If another running program opens one of those files at the same moment — typically to scan it, back it up, or sync it — the update hits a locked file, gives up, and reports 0x80070020 instead of telling you which program got in the way.

The usual suspects line up in a predictable order. Real-time antivirus is the runaway leader: scanners from Norton, McAfee, Bitdefender, Kaspersky, and even Windows Defender itself love to latch onto files the moment they change, and update files change a lot during an install. Next come third-party system utilities — disk cleaners, file-sync tools, backup agents, and "optimizer" software that hooks into system folders. Finally, a corrupted Windows Update cache can leave phantom locks of its own: the cache believes a download is still in progress long after it died, so every new attempt collides with a ghost of the old one. Your fixes should follow that same order — suspect the antivirus first, then background programs, then the cache.

Common causes

• Antivirus real-time scanning: third-party antivirus (Norton, McAfee, Bitdefender) or Windows Defender's own real-time protection locking update files mid-write — the most common trigger by far.
• Background system utilities: backup agents, file-sync tools, disk optimizers, and "PC cleaner" apps that hook into Windows system folders and hold files open.
• A stale or corrupted update cache: the SoftwareDistribution or Catroot2 folder contains a half-finished download whose lock never released, blocking every retry.
• Conflicting third-party services: services installed by hardware utilities, VPNs, or security suites that start with Windows and interact with update files.
• A half-completed previous update: an earlier update that failed or was interrupted can leave Windows Update in a broken state where new files cannot be staged.

How to fix error 0x80070020 — step by step

Work through these fixes in order. Step 1 is free and resolves many cases; step 3 identifies the most likely culprit; the last two cover stubborn, cache-related blocks.

1. Restart your PC and try the update once more. Save your work, restart the PC normally (not Shut down, which can hibernate instead of rebooting), and run Windows Update again right after logging in. File locks are often held by background processes that only restart in odd moments — a fresh boot clears them all, and this single step resolves 0x80070020 in a surprising number of cases.
2. Run the Windows Update troubleshooter. Open Settings, go to Update and Security (Windows 10) or System (Windows 11), then Troubleshoot > Other troubleshooters, and click Run next to Windows Update. The troubleshooter scans for stuck services, corrupted download caches, and misconfigured update settings, and it applies its own fixes automatically — including releasing locks on the update data stores.
3. Temporarily disable your antivirus, then retry the update. Right-click your antivirus icon in the system tray and choose Disable or Turn off protection for 10-30 minutes. If you use Windows Defender, go to Settings > Update and Security > Windows Security > Virus and threat protection > Manage settings and turn off Real-time protection. Run Windows Update immediately while protection is off — if it succeeds, your antivirus was the culprit, and you can re-enable protection right after. As a longer-term fix, add Windows Update exclusions or switch to a less aggressive real-time scanner.
4. Clean boot to find the program holding the lock. Type msconfig in the Start menu and open System Configuration. On the Services tab, check Hide all Microsoft services, then click Disable all, and on the Startup tab open Task Manager and disable every startup item. Restart — now only Microsoft services are running — and try the update. If it works, re-enable your services and startup items in small groups, restarting between each batch, until the update fails again; the last group you turned on contains the program that was blocking the files.
5. Reset the Windows Update components. Open Command Prompt as administrator and run net stop wuauserv, net stop bits, net stop cryptSvc, and net stop msiserver, then rename the update caches with ren C:\Windows\SoftwareDistribution SoftwareDistribution.old and ren C:\Windows\System32\catroot2 catroot2.old. Restart the services you stopped with net start wuauserv, net start bits, net start cryptSvc, and net start msiserver. This rebuilds the folders Windows Update downloads into, eliminating any file the old cache had locked.
6. Download and install the update from the Microsoft Update Catalog. Open Settings > Windows Update > View update history and note the KB number that failed. Go to catalog.update.microsoft.com, search that KB number, download the version matching your system (x64 for most PCs), and double-click it to install. Catalog installers use a different delivery path that bypasses the locked update agent entirely, so they succeed where automatic updates repeatedly fail with 0x80070020.

Did this fix it? Quick checklist

• PC restarted fresh, and the update retried with nothing else running
• Antivirus temporarily disabled — update tested while protection was off
• Clean boot identified (or ruled out) a third-party locking program
• Update components reset, or the KB installed from the Microsoft Update Catalog

If 0x80070020 keeps returning no matter which steps you try, open Resource Monitor (search for it in the Start menu), go to the CPU tab, and type part of a filename from the failing update into the Associated Handles search box — it will show you exactly which process is holding the lock. Persistent file-locking across many files can also mean a failing drive, so run chkdsk C: /f /r from an elevated Command Prompt if you see disk errors alongside the update failures.