There are issues involving an endless reboot cycle that starts after some HP systems are updated to Service Pack 3.
http://www.crn.com/software/207602807
Evidently, it has something to do with the OEM XP image HP put on some AMD-based desktops:
http://tinyurl.com/6zs52d
I’ll bet that over at HP Tech Support right now, you can hear the name Microsoft and the ‘F’ word used together quite frequently. 😉