Something to compliment this article.
The services.msc being mentioned are a great start but (for me at least) it was confusing at first figuring out what I needed.
www.blkviper.com is made by a guy in college (if he's still in college) and it has what every service does and his recommendations on whether you need to keep it Automatic, Manual, or Disabled. This helped me a lot when I use to be tweaked on computer tweaking. =P The site is down for construction (02/15/2006) but should be coming back soon God willing. Thanks for the article!