how can i create and login as "local service" or "system" in W2k

how can i create and login as "local service" or "system" in W2k
(winXP, win 2003 server , win 2000)
when i tried to creat a user acount named "local service" or "system"
windows said that this user is already exsist.
i know that these user account cannot be created in W2k but someone
says that he foud a bug in windows that allows you to creat those.
he is a MCSE. i want help specifically Micorsoft professionals !!!
everything you say will be useful.

thanks in advance