I've just read through all 6 pages of this thread and decided I needed to sign up and see if you can help. This is my first post so I apologize if I do anything odd.
I have isolated it to a Microsoft Wireless Keyboard and Mouse. With it connected to a USB port my AMD Athlon running XP Home Edition hangs on the "Windows is Shutting Down" screen. If I unplug the keyboard and use a PS/2 type keyboard and mouse it shuts down fine. I have also tried changing the power option on the USB port, and tried it in several other USB ports. Anything else you come up with would be greatly appreciated, it's very frustrating.:sad: