started having issues with running vista on my mpb

i run vista using bootcamp. it was giving me no problems until it completely froze on me earlier. now when i try and boot windows it goes to the screen to enter my password and all that. but after that the screen stays black. i can move the cursor, but that's it. anybody had this problem or know what i need to do? I'd like to avoid having to delete and reinstall because i have a lot of stuff saved on there. nothing too important. but still thing's i'd have to re-do.
TIA

Maybe it's an update gone sour...

Try to boot into safe mode and set windows back to last back-up.
I believe it's called system restore.