Hi,
I recently encountered a computer that won't shut down, it is a dell desktop running windows xp, The computer saves settings then sits on windows is shutting down indefinitely. I have run antivirus programs, and the computer works fine when it is running, but I can't get it to shut down. I tried googling the issue, but the sheer number of possibilities is kind of overwhelming. What other information do you need/want, and any help would be greatly appreciated!
Another method I use sometimes is to start Task Manager, select Processes then start the shutdown. Watch and see what processes get closed. After a bit, once you are sure the shutdown is hung, start killing processes one at a time until you find the one causing the hang.