Gentlemen, I ahve encountered this issue before, but the resolution used then isn't working now.
In short, WinXP Home (SP3) box is booting properly but A/V & Windows update, while appearing on the task bar, are not starting correctly. When I check services, Windows Update & Background Intelligent Transfer aren't there. Tried to reinstall as per these instructions on MS site, not no change (tried Service Pack folder in %windir%, then SP3 CD (not the proprietry one which came with the tower (Compaq) as cust. can't find.
Also tried a program I have used successfully before called dial-a-fix (sounds pretty sus, but works a treat) and it couldn't complete successfully as it has before.
NOD32 & MBAM indepth scans have been run in case there is a bug in the system - nothing found.
I welcome your thoughts!