A clean install is always better than an upgrade. I went the upgrade path because I didn't want to start reinstalling the world.
My first attempt took 2 hours before I got a blue screen. Luckily, Vista backed out gracefully and XP came back. A two hour call to Microsoft yielded very little as to why I blue screened. At their suggestion, I disconnect my turned off scanner, printer, card reader and tablet. I also uninstalled the NVidia video drivers as well.
The second attempt went fine. After the install, I reconnected everything and installed the NVidia video drivers. Still have no idea what happened the first time.