Visual Studio 2008 Hotfixes and SP1 Beta
Before installing VS 2008 SP1 Beta, check if you had installed any previous hot fixes. If yes, then you need to install the Hotfixes Cleanup utility before installing the SP1 beta.
Where to get the cleanup utility? Visual Studio 2008 Hotfix Cleanup Utility for Installing Visual Studio 2008 SP1
Hope this helps,
Regards