There is a lot of information available out there on what certain Windows services do and whether or not they can be safely disabled. For an excellent and actively updated guide for services in each of the current Windows releases, check out these guides on BlackViper’s web site:
While there are many other sites out there which offer the same information, I have found these guides to be the most concise and helpful.
One word of advice regarding tweaking services: while a few are hogs (i.e. the indexing service), most services do not consume a noticeable amount of system resources so disabling them wouldn’t really give you much benefit. If you are unsure if you need it, just leave it on.

Jason Faulkner is the man who brings you our daily tips. He is based in Atlanta, Georgia.