windows networking question – sort of

I have an old server (MS Server 2K) that I want to upgrade/refit. When I turn the server off one of our admin machines goes into zombie mode. It takes about 1-2 minutes to open any file or even a right click menu. Turn the server back on, all is well again. This machine has a TON of programs on it. I would like to avoid rebuilding it (xp sp2). How do I figure out which program is pointing at that old server?