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In-place upgrade repair: when it is worth the 40 minutes

Verified 2 min read

How a repair install differs from a reset, what it keeps, and the two failure logs that tell you why it stopped.

Tested onPro (26H2) / Server · Build 26300.9457 / 26100.33650 · x64
E1
Build
26300.9457 / 26100.33650
Edition
Pro (26H2) / Server
Architecture
x64
Support
Documentation (E1)
Evidence
E1Official documentation
Verified
2026-10-29
Page type
Method

The short answer

Section titled “The short answer”

An in-place upgrade reinstalls Windows over itself, keeping files, settings and most applications. It is the repair you want when:

  • sfc and DISM cannot fix corruption,
  • the component store is broken beyond repair,
  • an update repeatedly fails and uninstalling it does not help,
  • and you cannot afford a clean install.

It is not a reset. A reset removes apps; an in-place upgrade tries to keep them.

What it keeps and what it loses

Section titled “What it keeps and what it loses”
Kept Often lost
Files and folders some drivers (reinstalled)
User accounts and profiles apps with incompatible installers
Most desktop apps apps that hook the shell deeply
Windows settings some default app associations
Activation (digital licence) third-party antivirus (usually removed)

Take an image or at least back up the documents folder. “It keeps files” is a design intent, not a guarantee.

Prerequisites that decide success

Section titled “Prerequisites that decide success”
  1. Same or newer build — the media must not be older than the installed build.
  2. Matching language and edition — different edition means it becomes an upgrade, not a repair.
  3. Free space — roughly 20GB plus the size of the old install.
  4. Disable third-party antivirus for the duration.
  5. BitLocker suspended — the upgrade reboots several times.
Terminal window
# what you are running now
Get-ComputerInfo | Select-Object WindowsProductName,WindowsVersion,OsBuildNumber,OsArchitecture
# suspend BitLocker for the duration (re-enables after N reboots)
Suspend-BitLocker -MountPoint C: -RebootCount 3

Run it

Section titled “Run it”

From mounted media or an extracted ISO:

Terminal window
# from the root of the installation media
.\setup.exe /auto Upgrade /DynamicUpdate Disable /ShowOOBE None
  • /DynamicUpdate Disable avoids waiting on network updates mid-setup.
  • /ShowOOBE None skips the out-of-box experience.
  • Without switches, the GUI offers Keep personal files and apps — that is the repair option.

If the option to keep apps is greyed out, the media does not match the installed edition/language. Fix the media, do not force it.

When it fails, read these

Section titled “When it fails, read these”
Log Location Contains
setupact.log C:\$WINDOWS.~BT\Sources\Panther\ the whole setup trace
setuperr.log same folder only the errors
setupact.log (rollback) C:\$WINDOWS.~BT\Sources\Rollback\ why it reverted

setuperr.log is short; start there. Common causes: a driver blocking the upgrade, insufficient space, a language mismatch, or a pending reboot that was never completed.

After it finishes

Section titled “After it finishes”
  1. Check winver — the build should be identical or newer.
  2. Confirm activation: Settings → System → Activation.
  3. Reinstall the drivers that were removed (GPU, chipset, printer).
  4. Resume BitLocker and verify protection: manage-bde -status.
  5. Run Windows Update until clean.

When a clean install is the better answer

Section titled “When a clean install is the better answer”
  • The machine is being handed to someone else.
  • The profile itself is corrupt (a new local profile and migration is the fix).
  • You want a known-good state and have backups.
  • The upgrade failed twice at the same stage.
Section titled “Related”

Lab boundary

Section titled “Lab boundary”

E1. Setup switches and behaviour are Microsoft-documented. No repair upgrade was run on the lab VMs for this page.

Sources