citat:
http://support.microsoft.com/kb/948465
Removing the prerelease version of SP2
The prerelease version of SP2 is time-limited software. You must remove the prerelease version of the service pack before you install the final version of the service pack. Also, this software will no longer operate after May 1, 2010. You must remove the prerelease version of SP2 before that date.
To remove the prerelease version of SP2 for Windows Vista and for Windows Server 2008, follow these steps:
Click Start
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, copy and then paste (or type) the following command in the Start Search box, and then press ENTER:
appwiz.cpl
Click View installed updates.
Click Service Pack for Microsoft Windows (KB948465), and then click Uninstall.
Follow the instructions to complete the removal process.
For more information about how to remove Windows Vista service packs, click the following article number to view the article in the Microsoft Knowledge Base:
948537 (http://support.microsoft.com/kb/948537/ ) How to uninstall Windows Vista service packs as a troubleshooting step