As a proud ex owner of Stojadin (free translation of this car's nickname among the people was - hundredth miseries), I just had to post this! You better believe it. No special effects. :)

With over 134 system services running in Windows Vista, it wouldn’t hurt to disable the ones you really don’t need. Since there is a ton of shitty websites with all sort of guides for tweaking Vista, to make this blog post short - I will just state the best guides. If you are aware of more good ones, please feel free to post them.

http://vistarewired.com/2007/02/18/disable-services/
http://www.xcontact.ro/windows-vista-services-tweaks-69.html
http://members.rushmore.com/~jsky/id31.html
http://vistahelp.blogspot.com/search/label/Disabling%20Services%20Guide

It seams that the firefox 2 release has memory leak problems. I discovered the problem recently when I saw that my firefox was using more than 150 mb of ram after starting with 30 mb of ram. After some surfing I came across this fix, it basically clears the memory on firefox window minimize actions. The method is as follows:
Type about:config in to your address bar (these are firefox hidden settings), then right click and create a new boolean variable with the name config.trim_on_minimize and give it a value of true. That's it, every time you minimize your firefox window it will free the memory it uses.