I've loaded SP2 on several Vista boxes with no problems. Sounds to me like something went south on you during your installation process. I've had it happen before with WinXP, Linux, Solaris, you name it. Personally I'd give it another whirl or better yet, update to Windows 7 when it comes out next Thursday (supposedly.)

BTW, sounds like you've lost a hard drive full of data sometime before; most people get the back-up religion after going through that one time.

Cheers,
Bill