Dont go for a clean install right off the bat(IHMO) I had the same the problem with my desktop when i recently got it. For some reason it would never Auto Enable Norton AV, even when I had the AV on autostart. So I had to enable the auto startup from the Services mgmt console. I recommed you try that before you do a new install.
Also for unnecessary services that a home user might not need, try these links :
http://is-it-true.org/nt/utips/utips76.shtml
http://www.blkviper.com/WinXP/servicecfg.htm