While there is a fairly large amount of info about securing windows XP on AO... I didn't find to much on the services. I had to instead go thorough one by one and research them. That was OK, becasue I leared a lot.

I found that most of them were carried over from NT4 and 2k, but there were some new ones.

One of the best sites I've seen for service configuration/explanations is

Windows XP Home and Professional Service Configurations
This is also available in a pdf format and is a lot easier to read. Print it landscape though.

This site goes through virtuall every service that Windows Home and Pro has and explains what they are used for and if you will need them.

It is much better than searching for each service individually.