I have a computer (Dell OctiPlex) that can't get past the Windows user log on. It rejects the correct administrator password as "invalid", and it rejects the guest log on as "account disabled" even though there is no password required for the guest to log on to the desktop. Complicating matters is the fact that I can't log on in Safe Mode with Command Prompt. It keeps going to that log on screen. I tried to boot with the Windows CD to do a repair but much to my frustration it goes to the same user log on screen instead of the blue screen menu. No viruses were found on the HD when I scanned it with my other computer. All hardware appears to be working fine too. Reinstalling Windows is always a last resort. Any ideas before I resort to reinstalling?