How to Uninstall the Vista SP1
You can remove SP1 by using either Programs and Features or the command line. Note, however, that you cannot uninstall SP1 offline using any method. In addition, it is not possible to uninstall the permanent prerequisite updates (KB937287, KB935509, and KB938371). However, you can uninstall KB936330 and KB937954. You also cannot uninstall the service pack and other updates that were installed using an integrated installation.
For more information, see: Microsoft Help and Support: KB948537
To Uninstall SP1 by using Programs and Features
1. Open Control Panel, click Programs, and then click View Installed Updates.
2. In the Microsoft Windows list, right-click Service Pack for Microsoft Windows...