I just took the route of replacing XP with Win7 on one of my Compaq systems.
Fortunately I had removed the XP disk and replaced it with another "Just in case", turned out to be a good move. After loading Win 7 I quickly realised that this was Vista with a pretty new coat, same crud underneath. Now, no network connectivity, no sound, indexing everything by default keeps slowing it down and so on, it feels so much like Vista. I had tried the early betas, same issues, you kind of hope the final version is way beyond the beta stage.
Just as an exercise I loaded Ubuntu client, surprise, surprise, network worked, sound seemed fine and it ran twice as fast, I know where the "upgrade" for this system is headed, NOT in Win 7 direction.
XP disk replaced and the windows world worked again.
BEWARE.
pmills575