FWIW, here are some comments regarding a OS change from NT 4.0 to XP.

Just installed XP in a machine that had NT 4.0 and many problems.

PROS:
Visually very appealing, installation ran without a hitch.

CONS:
Slower internet access than Win2K, at least for UT.
Very expensive, even an upgrade from NT 4.0, supposedly within the same family.
Location of things is shuffled... again. To get the vanilla explorer I am running it from Start/Run!

CONCLUSIONS:
XP is a a good product.
Not worth updating machines that run reasonably well.
MS doesn't just own Windows, it owns us, the users.
Learn Linux.