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Error 0xC1900101 - the Windows upgrade keeps rolling back

0xC1900101 is the code Windows shows when an upgrade to Windows 10 or 11 fails partway and rolls itself back - often after a long wait and several restarts. Microsoft's documentation is unusually direct about this one: 0xC1900101 is commonly a driver error. A storage, graphics or Wi-Fi driver that the new Windows cannot carry over stops the whole upgrade. Bring the drivers current, clear the usual obstacles, and the upgrade goes through.

Fix it automatically

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Quick answer

Update all drivers (storage, graphics and network first), unplug every non-essential USB device, make sure the system drive has 20+ GB free, temporarily uninstall third-party antivirus, then run the upgrade again. That checklist clears the overwhelming majority of 0xC1900101 rollbacks.

Symptoms - how this problem looks

The upgrade fails with 0xC1900101 - 0x20017, 0x30018, 0x40017 or similar
Windows installs for an hour, restarts, then returns to the old version
"The installation failed in the SAFE_OS phase" or "SECOND_BOOT phase"
Each retry fails at roughly the same percentage or restart
The PC is a few years old and has never had a full driver refresh
Docks, hubs, external drives or an old printer are plugged in during the upgrade

Why it happens

A driver the new Windows cannot carry over

The upgrade migrates every installed driver. One outdated or broken driver - storage and graphics are the classic culprits - crashes the migration and triggers the rollback.

Peripherals confuse the setup

Every plugged-in device brings its driver into the upgrade. Docks, hubs, printers and external drives multiply the chances that one of them fails the migration.

Not enough free disk space

The upgrade keeps the old Windows aside for the rollback, so it needs room for two systems at once. A nearly full drive fails late in the process.

Security software holding files

Third-party antivirus drivers hook deep into the system and are a documented source of C1900101 failures - temporarily removing them is part of Microsoft's own checklist.

The fixes, in order

1. Bring every driver current (the main fix)

  1. Right-click Start, open Device Manager, and look for any device with a yellow triangle - fix those first (Update driver, or remove the device).
  2. Update the storage, graphics and network drivers: right-click each, Update driver, "Search automatically" - and check the PC or motherboard maker's site for anything newer.
  3. Also install every pending update in Settings, then Windows Update, including optional driver updates.
  4. Restart before retrying the upgrade.

2. Unplug everything non-essential

  1. Disconnect USB drives, docks, hubs, printers, card readers and any other peripheral - keep only keyboard, mouse and monitor.
  2. On a laptop, run the upgrade on mains power.

3. Free up disk space

  1. Open Settings, then System, then Storage - make sure the system drive has at least 20 GB free.
  2. Run Disk Cleanup (cleanmgr), tick "Previous Windows installations" and temporary files if offered.

4. Temporarily remove third-party antivirus

  1. Uninstall the third-party antivirus (not just disable - its drivers stay loaded otherwise). Windows Defender takes over automatically.
  2. Reinstall it after the upgrade completes.

5. Repair the system and retry

  1. Right-click Start, open Terminal (Admin), run sfc /scannow, then DISM /Online /Cleanup-Image /RestoreHealth, then restart.
  2. Run the upgrade again - via Windows Update or the Installation Assistant from microsoft.com.

Good to know: a 0xC1900101 rollback does not touch your files or programs - Windows returns exactly as it was. Fix the cause from the list above and simply run the upgrade again; there is no need for a clean install on the first failure.

Frequently asked questions

The code has a suffix like 0x20017 or 0x30018. Does it change the fix?

The suffix tells which upgrade phase failed, but the practical checklist stays the same: drivers first, then disconnected peripherals, disk space and security software. All 0xC1900101 variants share the same root family - a driver the new Windows cannot carry over.

Which driver is the one breaking my upgrade?

The usual suspects are storage, graphics, Wi-Fi and very old peripheral drivers. Windows does not name the culprit in the error itself, which is why the reliable route is to bring every driver current before retrying rather than guessing at one. The driver update guide walks through the manual way.

My files - do they survive a 0xC1900101 rollback?

Yes. This error happens during the upgrade and Windows rolls back to the previous version automatically; your files and programs stay as they were. It is frustrating but not destructive - fix the cause and run the upgrade again.