Windows Installer not working.

OK, I removed the Nimda virus from my Win 2000 Server and now Windows Installer will not work. I done all the suggested procedures; renamed the msiexec.exe file and related dll files and reinstalled using the latest version. No good! I get no help other than a Windows generic 1015 error suggesting possible registry problems. I’ve reinstalled the OS, after formatting the partition, I’ve used Nortons to scout for obvious errors, I’ve tried other versions of the Windows Installer. Help!!!! It seems to be either registry or some permissions that I can’t find, not allowing Installer to operate.