Win 2K REFUSES TO ACCEPT ANY PASSWORDS what gives?

I have a computer with password issue… it has a mind of its own. Despite a fair amount of websurfing I can’t seem to solve the problem. When booting in both normal & safe modes it rejects the password for both user and adninistrator by returning to the login screen. I have Win2k pro plus Sp4 installed and AVG virus-ware loaded..
I’m wary of rebooting the setup Win2k CD because I have a dual boot system,with Win98se loaded, which, by the way works fine as it doesn’t require a password.
Question:- Should I boot the setup CD in win 98 mode and reload…? I hope there’s another simpler way as I’d hate to lose all my settings etc.
Thanks for any assistance.