i use xp manager, jv16 powertools and sisoft sandra professional.
xp manager has alot of tweaks and cool **** like information,optimizer, cleaner, customization, security, network, and misc utilities. its a ton of stuff u can do to xp all in one.
jv16 is just a good utility with alot of tools
sandra prof. can tell me so much about my computer along with benchmarking and other way cool stuff. heres a screenshot of sandra http://www.jaggedonline.net/images20...SP1screens.jpg
actually it has like all the specs for other hdds, cpus, memory etc so when u test ur box u have something to compare it to, thats what that pie graph pentagon thingy is in that pic
alot of these are shareware but are limited versions, i have full versions of all and am happy with each
edit, and i use zonealarms cache cleaner to get rid temp. internet files, index.dat files, run/search/url etc history, and also adaware 6.0 prof. and spybot s+d