http://www.ccleaner.com/
Id use this to check what is loading on startup.
http://www.spywareinfo.com/~merijn/programs.php
Also this is the daddy of stopping stuff starting, but u can easily break the OS. There are some good links from this site. One link gives a list of programs to run to stop spyware getting on ** pc in the first place.
I use Adaware, spyware s&d, and spyware blaster.
Says the same thing in the sticky that was linked to in previous post:
Programs you just shouldn’t do with out
Link provided for each one
1. Ad-aware: Get the latest version, do an online update and do a good scan of your system for spy and ad ware. Very good for keeping your system clean and at optimal performance.
2. Spybot Search and Destroy: Picks up some stuff ad-aware doesn’t.
3. RegSeeker: Scans the registry for invalid entries. Good for a cleanup and optimisation of your registry.
4. Tweak XP: Full of all kinds of good and useful tweaks and changes to Windows. Very cool little app, handy to have.
5. Tune XP: Some good tune up tweaks including a good one for reorganising boot files to save some time. Link includes a review of the program
I wouldnt mess with the services too much, and system restore is one of windows xp's best features so I wouldnt disable that.