windows 2000 won't log on

I have had problems with a virus latly and have tried many things to remove it all unsuccesfuly. I downloaded the most recient service pack for windows 2000, and ran spybot search and destroy, and spydoctor. Both returned winlogon.exe was a thret so I removed it.

After doing so I now relize it probably was a mistake.

When I try to turn my computer on It keeps rebooting in a loop. I get the start up page to load but when it attempts to log onto windows the computer restarts, and keeps doing this over and over.

I have tried starting it is safe mode and every other available mode and nothing works.

thanks for your help
reesel