as GR@PH;<'S says, most utilities are meant to help your system, and will not harm your box...BUT you need to understand what the program is doing...read the manual so to speak...make sure you want the program to do what it's intended to do.
example, as lechtard posted, ram releasing utilities will slow xp down, no matter how you use the program
GR@PH;<'S ...you'll get a kick out of the great free programs
way back when I started that thread, adaware was on the first post.
now that thread has hundreds of incredible free utilities...ad free was a must for the program to be posted.