Microsoft has released Service Pack 3 for Windows XP. Unsurprisingly, it's having some problems.
The biggest problem is that some systems reboot endlessly, ending in blue screens every time. Microsoft says in KB888372 that this happens when an AMD-based system has a disk image originally developed on an Intel-based system. Apparently, many HP systems did this, although HP wasn't commenting. This configuration dies in SP3 because that section of the registry isn't used anymore ("orphaned"), and the system ends up trying to load both the AMD and the Intel drivers. Bad things happen after that.
This shouldn't be a problem with Dell computers, they stick to Intel - but keep it in mind for any AMD-based XP systems you know about. The KnowledgeBase article, I'm told, has instructions for preventing this from happening, or for fixing it afterwards, provided you can find away to boot into Safe mode.
Good luck and get a Mac or Linux-Based system.