Virus update results in looping reboot

Im running windows 2000 .I recently updated my NAV definitions using Live Update. I was asked to reboot , it did as usual and boots up all the way to where its applying security settings and then loops back into a reboot again . It will boot into safe mode.
Is there a way to rewind 2000 like on ME? Can I edit the file that controls rebooting ? Can I blame NAV? Anyway any help would be greatly appreciated…..

Thank you in advance , Darren Moeller