Password lost how do I get in to 2000

Here’s a sticky prob. One of our employees left and moved to the carribean, before leaving to show his disgruntlment he changed the password on Win 2000, now we can’t get in. We tried to do a cold boot but no joy, the info on his PC is of no importance so we would like to format the drive and reload Win 2000. So far we have had no luck.. Any suggestions are more than appreciated.
Unhappy.. Dave