Problem shutting down windows xp...system query not respon.

I have a Dell system running windows xp. Every time I shut down the computer, I get a message saying... "Ending program - System Query". After a few seconds, it says "Program not Responding" and I can choose to End Now and the computer will shut down, or I can Cancel. Why does this come up every time I shut down the computer, and how can I fix this problem?
Thanks in advance.