In this episode of Defrag Tools, we talk about the Windows Upgrade Log files. The "Panther" logs track the installation of a Windows Upgrade. The logs contain Information, Warnings and Errors. Not all errors are fatal, the trick is to look at only the (last) fatal error if an upgrade fails. The logs pre/post upgrade can be found in: \$Windows.~bt\sources\panther \$Windows.~bt\Sources\Rollback \Windows\Panther \Windows\Panther\NewOS You can review the logs manually, or use SetupDiag.