Man those things are annoying. It's like a giant toy box with all sorts of trinkets from grandfather's attic that he won't let you throw out or something.
Of course, tinker with them I have, and I'm glad that I made my profile log on much faster.
This is one of the sites I looked at:
Windows XP Services
What's more, I love how you can type the name of any service into Google and you're practically guaranteed to get REAL useful information on how the service affects your computer.