how to recover local admin password in win2000 server

Hai guys
this is vinod here. In our office there is a win2000 server os which is used as an antivirus server, it also connected to the domain i.e it is a member domain. we have forget the local admin password of this system problem is that the domain users have been removed from the administrators group. hence i am not able to perform any tasks like even changing an ip, acces is denied.

please help me out guys its urgent

regards
vinod.s