On two different occasions I was asked to help when VS 2005 would not load. We were able see only VS 2005 splash screen and that’s it. In first case the CPU usage by devenv.exe was 25%. To resolve this problem I launched VS in safe mode.
C:\Program Files\Microsoft Visual Studio 8\Common7\IDE>devenv.exe /SafeMode
This prevents all third-party VSPakages from loading. After that VS 2005 was loading properly all the time.
I believe that in both cases it happened after the developer installed an add-in.