How to fix Windows upgrade error 0x8007007f?

Error code 0x8007007f means Windows Setup tried to call a function in a DLL file and could not find it, so the upgrade to Windows 11 stops or rolls back. It is almost never a hardware fault. Start the Installation Assistant with Run as administrator after you clear old setup files, or upgrade from the ISO instead.

Facts checked on 15 October 2026. Steps written for Steps written for Windows 10 22H2 and Windows 11 25H2 and 26H2, against Microsoft's download page for Windows 11 version 26H2.

What error code 0x8007007f means in the Windows 11 upgrade

The full message in the Installation Assistant reads: "Something went wrong. Select try again and if that doesn't work contact Microsoft support for help. Error code 0x8007007f". The code itself is a Windows system error in a wrapper. The last part, 007F, is error 127, which Microsoft lists as ERROR_PROC_NOT_FOUND: "The specified procedure could not be found."

Why the Windows 11 upgrade fails with 0x8007007f

Microsoft has not published a single cause. A missing function means that Setup loaded the wrong copy of a DLL, a damaged one, or one it was not allowed to use. The ranking below joins what error 127 means with what Microsoft Q&A moderators and users report. Each cause points to a fix.

Where Windows Setup writes the real cause of 0x8007007f

If the upgrade got past the first screen, Setup keeps its logs in the hidden folder C:\$WINDOWS.~BT. Read them before Fix 2, because Fix 2 deletes that folder. A Microsoft Q&A volunteer moderator asks for exactly these files when helping with this error.

1. Press Win + R, type C:\$WINDOWS.~BT\Sources\Panther and press Enter.
2. Open setuperr.log in Notepad. Search with Ctrl + F for 0x8007007f and for gle=0x7f.
3. Look at the DLL named on those lines, for example WSManMigrationPlugin.dll or RasMigPlugin.dll in the Q&A case.
4. If the PC rolled back, also copy the C:\$WINDOWS.~BT\Sources\Rollback folder.
5. Zip setupact.log, setuperr.log and the Rollback folder to keep them for support.

How to fix error code 0x8007007f in the Windows 11 upgrade

Fix 1 and Fix 2 solve the common cases and change nothing outside the upgrade's own files. Fix 3 uses Microsoft's ISO instead of the assistant. Fix 4 to Fix 6 deal with drivers, other programs and system files, and Fix 7 tests a third-party security program.

Fix 1. Run the Installation Assistant as administrator from an administrator account

5 minutesNo riskYou started the assistant with a double-click, or you are not sure your account is an administrator.

Microsoft's download page says you need to be an administrator to run this tool. Without full rights, Setup cannot load some of its DLLs from protected folders, and a missing function shows up as error 127, 0x8007007f.

1. Press Win + I and open Accounts > Your info. Under your name it must say Administrator.
2. If it says Standard user, sign in with an administrator account, or ask the owner of the PC to change your account type.
3. Close the assistant if it is open. Download it again from Microsoft's Download Windows 11 page.
4. Right-click Windows11InstallationAssistant.exe and select Run as administrator. Step by step: How to run a program as administrator or in compatibility mode.
5. Select Yes in the User Account Control prompt and let the assistant check your PC.

Fix 2. Delete the files of earlier upgrade attempts and free 9 GB on drive C

15 minutesLow riskYou tried to upgrade before, the PC rolled back once, or drive C has less than 9 GB free.

A Microsoft Q&A volunteer moderator's first step for this error is to delete C:\$WINDOWS.~BT, C:\$WINDOWS.~WS and C:\ESD and run Setup again. Half-written files from a failed attempt can hold a wrong copy of the DLL that Setup then loads.

1. Copy the logs first if you may need them, as in the section on where the cause is written.
2. Close the assistant. Press Win + R, type cleanmgr and press Enter. Choose drive C:.
3. Select Clean up system files, choose drive C: again and wait for the list.
4. Check Temporary Windows installation files and Windows upgrade log files, then OK and Delete Files. Step by step: Free up disk space and delete temporary files.
5. In File Explorer select View > Show > Hidden items (on Windows 10 View > Hidden items). Delete C:\$WINDOWS.~BT, C:\$WINDOWS.~WS and C:\ESD if they are still there.
6. Check in This PC that drive C has at least 9 GB free, restart the PC and run Fix 1 again.

Fix 3. Upgrade from the Windows 11 ISO with setup.exe

1 to 2 hours, mostly download and installLow riskThe Installation Assistant fails every time, and you only want Windows 11 on this PC.

The ISO contains the full Setup, so nothing is assembled by the assistant on your PC. Microsoft's page says that mounting the ISO performs an upgrade of your current system, and the Q&A moderator suggests the ISO because it can be reused for another attempt.

1. Back up the files you cannot lose: Back up your files (Windows Backup, File History, Time Machine).
2. On Microsoft's Download Windows 11 page, under Download Windows 11 Disk Image (ISO) for x64 devices, choose the edition and your language, then 64-bit Download.
3. Right-click the ISO file and select Mount. If Mount is missing, open Properties, select Change next to Opens with, choose Windows Explorer and Apply.
4. Open the new drive in File Explorer and double-click setup.exe.
5. Follow Setup. Under Choose what to keep, select Keep personal files and apps, then Install.

Fix 4. Update the graphics driver and remove incompatible drivers

15 minutesLow riskThe graphics driver is old, Memory integrity lists incompatible drivers, or the upgrade fails after the first restart.

Drivers load their own DLLs during the Safe OS phase of the upgrade, where SetupDiag reported 0x8007007F-0x2000A in the Q&A case. The moderator checks Memory integrity for incompatible drivers before any new attempt, and users report that a new graphics driver alone fixed the error.

1. Open Windows Security > Device security > Core isolation details. If it lists incompatible drivers under Memory integrity, note their names.
2. Update or remove each listed driver from the maker of the device, or in Device Manager: Update, roll back or reinstall a driver.
3. Install the newest graphics driver from NVIDIA, AMD or Intel, or from the PC maker's support page.
4. Press Win + I, open Windows Update > Advanced options > Optional updates (on Windows 10 Update & Security > Windows Update > View optional updates) and install the driver updates there.
5. Restart the PC and run the upgrade again, as in Fix 1 or Fix 3.

Fix 5. Start Windows with a clean boot and run Setup again

15 minutes plus the upgradeLow riskThe upgrade reaches a percentage, restarts and rolls back, or the log names a migration plugin.

Third-party services and startup programs can load their own DLLs into Setup's processes. The Q&A moderator advises a clean boot before an in-place upgrade so that only Microsoft services run while Setup loads its plugins.

1. Press Win + R, type msconfig and press Enter.
2. On the Services tab, check Hide all Microsoft services first, then select Disable all. Step by step: How to perform a clean boot in Windows.
3. Disable the startup apps in Task Manager, select OK and restart the PC.
4. Run the assistant as administrator, or setup.exe from the ISO, and let the upgrade finish.
5. After the upgrade, open msconfig again and select Normal startup.

Fix 6. Repair Windows system files with DISM and SFC

20 minutesNo riskSFC or DISM has not run yet, or other programs also report missing functions or DLL files.

Setup copies parts of your current Windows into the new one. If a system DLL is damaged or a wrong version, the function Setup looks for is missing. The Q&A moderator runs these two commands when the log names a DLL in C:\Windows\system32.

1. Open Command Prompt as administrator.
2. Repair the Windows image first, then check the system files:

   dism /online /cleanup-image /restorehealth
   sfc /scannow

3. Restart the PC when both are done. Step by step: Run DISM and SFC to repair Windows system files.
4. If the log named a DLL, check that it exists, for example with dir C:\Windows\system32\WSManMigrationPlugin.dll.

Fix 7. Uninstall a third-party antivirus for the upgrade

15 minutesLow riskA security program other than Microsoft Defender is installed, and Fix 1 to Fix 6 changed nothing.

Security programs load their own DLLs into other processes and some guard the setup folders. The Q&A moderator advises uninstalling third-party antivirus before the upgrade and reinstalling it after. Microsoft Defender turns itself on while it is gone, so the PC stays protected.

1. Write down the program's name and your licence key or account so you can reinstall it.
2. Press Win + I, open Apps > Installed apps (on Windows 10 Apps > Apps & features), find the security program and select Uninstall: Uninstall a program or app in Windows.
3. If it will not uninstall cleanly, use the removal tool from the program's maker.
4. Restart the PC. Check in Windows Security that Microsoft Defender's real-time protection is on.
5. Run the upgrade, then reinstall your security program in Windows 11.

If error 0x8007007f still stops the upgrade

When a clean drive, an administrator start, new drivers and a clean boot do not help, the log decides what comes next. In the Microsoft Q&A case, the next attempt crashed while moving Store apps, and the moderator offered two ways out: reset the Store app repository, or back up and install with fewer things kept.

• What to send to support: the exact message, your Windows version from winver, and which fixes you tried.
• Add setupact.log, setuperr.log and the Rollback folder from C:\$WINDOWS.~BT, zipped.
• Microsoft's SetupDiag tool reads those logs and names the failing phase, as it did with 0x8007007F-0x2000A in the Q&A case.

How to keep error 0x8007007f away on the next upgrade

If the assistant shows a different message before anything downloads, see our guide to the Installation Assistant's "Can't create files" error, which covers the tool's own folder and permissions.

Frequently asked questions

What does error code 0x8007007f mean?

It means Windows could not find a function it tried to call in a DLL file. The last part, 7F, is Windows error 127, which Microsoft names ERROR_PROC_NOT_FOUND: "The specified procedure could not be found." In the Windows 11 upgrade it usually means Setup loaded a damaged, wrong or blocked copy of one of its files. The fix is to give Setup full rights, a clean start without old setup files, or a complete Setup from the ISO.

How do I fix error code 0x8007007f on Windows 10?

Most readers on Windows 10 see it while upgrading to Windows 11. Download the Windows 11 Installation Assistant again, right-click it and select Run as administrator from an administrator account. If it fails, run Disk Cleanup with Clean up system files, remove Temporary Windows installation files, delete the C:\$WINDOWS.~BT folder and make sure 9 GB is free. If the assistant still fails, mount the Windows 11 ISO and run setup.exe. Windows 10 left support on 14 October 2025, so finishing the upgrade matters.

Can I get 0x8007007f on Windows 11 too?

Yes. On Windows 11 it appears when you move to a newer version with the Installation Assistant or the ISO, for example from 24H2 to 25H2 or 26H2. The cause and the fixes are the same as on Windows 10: run the tool as administrator, clear the files of earlier attempts, update drivers and start Setup from a clean boot. Your installed Windows 11 keeps working while you try, because a failed upgrade rolls back to the version you had.

Will I lose my files because of error 0x8007007f?

No. When the upgrade fails with this code, Setup rolls back and your current Windows, files and apps stay as they were. Data is at risk only in the steps you choose later: an upgrade with Keep personal files only removes apps and settings, and a clean install removes everything on drive C. Back up your files before any further attempt, whichever tool you use, and keep the backup on another drive or in the cloud.

Is running the Installation Assistant as administrator really enough?

Often, but not always. Microsoft's download page says you need to be an administrator to run the tool, and many users report that Run as administrator removed 0x8007007f at once. It does not help when the error comes from old setup files, a driver or a third-party program that loads into Setup. If the error returns after an administrator start, go on to Fix 2, which clears the files of earlier attempts, and then to the ISO in Fix 3.

Is it safe to delete $WINDOWS.~BT, $WINDOWS.~WS and ESD?

Yes, when no upgrade is running or waiting for a restart. A Microsoft Q&A volunteer moderator advises deleting these three folders before running Windows 11 Setup again, and explains that C:\ESD is created only for the time of the in-place upgrade. Copy the logs from C:\$WINDOWS.~BT\Sources\Panther first if you may need them for support. Do not delete C:\Windows.old in the same step, because it lets you go back after a finished upgrade.

What does 0x8007007F-0x2000A mean in SetupDiag?

The first part is the error, a missing function. The second part, 0x2000A, tells you when it happened. In the Microsoft Q&A case SetupDiag reported the last phase as Safe OS and the last operation as running sysprep specialization on the new Windows. That phase runs after the first restart, when drivers and system plugins of the new Windows load. Start with Fix 4 for drivers and Fix 5 for a clean boot.

What is code erreur 0x8007007f or Fehlercode 0x8007007f?

It is the same error in French and German Windows. "Code erreur" and "Fehlercode" only mean error code, so 0x8007007f has the same meaning and the same fixes in every language of Windows. This page is in English. The menus are named the same way in translation: look for Run as administrator, Disk Cleanup and Clean up system files in your language, and choose your own language when you download the Windows 11 ISO from Microsoft.

Should I remove my antivirus or change UAC to get past 0x8007007f?

Keep User Account Control on, because the administrator start in Fix 1 depends on it. Do not leave the PC without protection either. If you use a third-party security program, the Q&A moderator advises uninstalling it for the upgrade and reinstalling it after. Microsoft Defender switches itself on when no other antivirus is installed, so the PC stays protected while you upgrade. Pausing or removing protection is the last test, not the first fix.

It still fails after every fix. What now?

Keep the logs, setuperr.log, setupact.log and the Rollback folder from C:\$WINDOWS.~BT, and read which DLL or phase they name. If Setup keeps failing at the same step, run setup.exe from the ISO and choose Keep personal files only: apps and settings go, but your files stay. Back up first. A clean install is the last option. On a work or school PC, ask the IT department, because policies may block the upgrade on purpose.