Windows Password/logon problems

We have a user on our network who has Win2000 as his OS. Somehow, he managed to password his Win2000 machine, and you guessed it, forgot the password. It would be easy enough to reset thru administrator, except that we can’t get past the windows logon screen even with the administrator password. Is there anything we can do to get in there?

Please forgive me if this has been asked before.