combofix Power Failure

I was running combofix on a windows XP Media Center OS. It went through the first part perfectly. Found the problems and deleted them. Then it had to reboot the computer. No problem reboot started and then Combofix just sat there. Waited 2 hours and then the power went out (UGGHH)..

Problem: When I try to log back into windows it trys to come up and then logs itself off. I tried this in safe mode / Safe mode with command prompt / and normal mode. Even if I try to login with Administrator .. It tries. The desktop background appears then it logs right back to the Login screen with the user accounts on it.

Sound like a reinstall of Windows?? Any ideas since I can't even get in.

Thanks