Search on the net for registry cleaner. It a simple program....just open tools->registry cleanup->do them all..........it finds all unneeded entries in the registry. Also you could check the front page for programs that you know you had and dont have any more and delete the entries.
Next ting....i need a listing of essential windows processes. I give them my laptop to configure for a new network in school....it wasnt achieving its potential before....it worse now. I hadda wait till school close to do the reinstall like i planning to...but in the mean time i want to know the processes you could do without so i go stop them from loading.
WC, here is the registry cleaner I use. I have found it to be very effective.
http://www.ccleaner.com/
Use the "Cleaner" and "Issues" option. Doh mess with de rest unless yuh know wat yuh doing.
I have found that the defaul option in Cleaner and Issues does a good job.
Also download "spybot search and destroy" to get rid of hidden programs.
http://www.spybot.info/en/spybotsd/index.html
Do me a favor stay away from mister spybot....it does miss a lot of things.........Jus get Symantec pro and yu should be ok. Go to any download site (Limewire, torrent sites) and they should have crack versions of it. Also you might want to do a google search for recent virus alerts and see what that brings up. They have new ones coming up all de time. 
Be careful downloading software from limewire, sometimes they ridden with viruses..
I use a virus scan right now called Kaspersky which handling me right up, you can try that but you'll have to find a crack for the key...
I think if you go to windows search and options, there something that loads a process to do faster indexing for searching which hogs resources as well.. Try disabling that too and free up space..
But all in all, a RAM upgrade will show you the biggest diff in performance..
