I’ve determined the cause of my recent PC problems, in which Windows XP gets hung up while rebooting: Windows XP Service Pack 3. I isolated the other variables and allowed Windows to download and install XP SP3 and reboot, and it never completed rebooting. It took another hour-plus to restore Windows to a pre-Service Pack 3 time when everything worked, and even with that I spent another half-hour reinstalling device drivers. Just another day in PC world. My fingers were itching to dial the Apple store during the entire ordeal.