I am one of the unlucky few to be having problems with the SP2 pre-release. I have followed the instructions on this link SP2 Prerelease Version - Uninstall many a time but every time get the message "reverting changes do not turn off your computer" i have tried turning off my antivirus while uninstalling but this made no difference. Can anybody be of any further help would be much appreciated.

1.Run cmd.exe with administrative previlliges (right click on cmd.exe as admin) and type:

sfc /scannow

2.Try suggestions from this article How to uninstall Windows Vista service packs as a troubleshooting step

if really nothing help run Readiness Tool Description of the System Update Readiness Tool for Windows Vista, for Windows Server 2008, for Windows 7, and for Windows Server 2008 R2

and next

1.Find CheckSur.log file in C:\Windows\Logs\CBS folder
2.Download and run RegBak Acelogix Software - Freeware

Create registry copy,from this copy concern me COMPONENTS file

Pack CheckSur.log and COMPONENTS file to *.rar format and upload on rapidshare.com