The only thing I can think of that may be doing it is the fact that when i hit Control+Alt+Delete, i have about a million apps running which i dont know about and that have funny names like "ashwebserver"
That suggests virussy trojanny spywarey things are still lurking to me.
You could try a different virus scanner (
www.nod32.com do a 30 day full-feature evaulation for free, which I have used before when Avast failed to spot stuff).
You could try googling for each process you see in task manager. There are
lots of sites that tell you what is essential to windows and what is not.
You can prevent stuff from running on startup by doing
Start->Run->msconfig
and unticking startup items, but not all os's have this.
You can manually prevent stuff from starting up by looking in the registry
(Start->Run->Regedit - only if you are feeling brave!)
under
HKEY_LOCAL_MACHINE/SOFTWARE/Microsoft/Windows/CurrentVersion/Run
and deleting anything suspicious (AFAIK Win2k and XP don't need anything under this registry key, but your printer driver etc might legitimately put stuff here).
Also (more obviously) in your start menu in the "Startup" folder AFAIK nothing is required by windows.
XP services can be enabled/disabled using msconfig (and it helpfully allows you to distinguish between MS ones and non MS ones).
You can disable 2k services by right clicking my computer and hitting "manage". If you disable an important MS service you may end up screwed.
Unfortunately, nastier things (MS ActiveSync for one :p ) will automatically reinsert themselves into the startup groups.
Starting in safe mode may allow you to edit them out while they are not running, I am not sure.
Disclaimer: you can *really* bugger up your PC by messing in the registry, and can probably do bad things to it if you disable essential services.