With windows 7 Beta now out making its treks XP’s days may be numbered; but for older computers it will most likely stay the viable choice.
I myself love XP and have been tweaking it, playing around and customising it for bet performance and security.
Below are a number of registry tweaks I use to maximise the ‘benefit’ of XP!

(to use the file rename it from .reg.txt to .reg only and double click).
EDIT: Due to a conflict with a plugin the tweaks are only available for download.