When I set up my Vista on this pc in a dual boot setup it was a resource HAWG. After a little searching I found this site which helped me to set the service and make it a lot leaner and less resource hungry than before. Check it out. You may like what you find, but please be very careful if your new to tampering with Windows services. You can cause yourself a lot of irritation by doing something wrong. http://www.blackviper.com/WinVista/servicecfg.htmhttp://www.blackviper.com/WinXP/servicecfg.htm
There are also links to streamlining your XP sevices. Again be very careful trying these. And I'll add that I tried both setups as they set them for "Tweaked" and it was perfectly fine.