I like this tweaker Tune XP from DriverHeaven (free)_
hxtp://www.driverheaven.net/dforce
good for arranging the boot files and defraging them.
Other stuff too
another freebie, the Tweaking Expereience, is from
_
hxtp://windowsxp.homedns.org/xp/asp/twg/twg.asp
and it comes with an uninstaller built in