boot problems, plleease help

Ok, now... I installed Pinnacle Studio 9 today and rebooted when it asked me to. Then, after it reboots and goes through the bios screen and windows loading screen, right before i get to desktop, it restarts my computer again. I have Norton GoBack which has helped me a lot in the past but even when I rolled back to an earlier date I still got the same problem. I booted into safe mode, it just hung at the "loading your settings" screen right before desktop... I tried safe mode with networking, this worked once but hung each other time, I also tried safe mode with prompt, which worked.. i tried running chkdsk on that but it said it couldn't fix anything because i was in safe mode... So now, I am stuck... I can't get to the desktop and the computer restarts each time... please please help as I have some VERY important info on my drive and wouldn't want to lose it. Thank you.

BTW, Rig:
xp pro
nvidia nforce 2
athlon xp 2500+
512 geil ram
good cooling