How do i delete qued emails in "exchange 2000" step by step please

We found a pc on the network sending out spam emails and are signed up with dyndns as a smart host.  Problem is that we have a limit to 1200 emails aday allowed to leave us...the infected pc has qued up alot more emails in the exchange waiting to go out tommorrow and we will hit our 1200 email cap.  We pulled the pc off the shelf and now how do we go into exchange 2000 and delete the queue of that mailbox. ?