Event Log and Remote Procedure Call (RPC) should never be changed regardless of what guides say. Most of the services are dependent on either Event Log and/or RPC so disabling these will cause almost every service to fail.
However, there are a couple good sites that can help you through this:
•Tweaking NT Services
•Windows 2000 Professional and Server Services Confiqurations
If you have any problems after applying these tweaks you may want to go back to the defaults, you can use these links that will tell you what the defaults are:
•Windows 2000 Services
For information and links specifically for Windows XP, please see the sister FAQ -- What Services can I change to speed up my system? (#2892)