W2K : update starts automatically and takes up 100% CPU resources

Hi,
hope someone can help...

When :
This only happened suddenly and the person who uses the PC normally (my
retired dad), couldnt tell me what he'd done.

Symptoms :
Applications were slowing down, and the mouse was jumping all over the
screen erratically. Eventually, I noticed a 'downloading updates' icon in the
system tray and that led me to check for the update process. I realised that
the update.exe process was taking up 100% of CPU resources.
I couldnt end the process from the task manager either, and there were
apparently no startup items that fired up update.exe.
Earlier, when I went to windowsupdate.microsoft.com to check for updates
that my PC needed (stage 1 of the check), the check never came back.
Although when i clicked on the link for 'update history', it could return me
the list of updates that I'd installed.


Action Taken :
I then turned off automatic updates (Norton as well as control panel),

Result of Action :
update.exe process still started automatically and was still taking up 100%
of CPU resources just after I booted up.

Subsequent Desperate Further Action :
Eventually, I had to go to Services and Disable 'Automatic Updates' to
prevent it from even starting after I boot up.

Results :
Update.exe didnt start upon booting. (yay?)
No more hogging of resources, and my mouse and processes were ok again.

Annoyance :
Somehow I feel that didnt solve the problem, merely avoided it for awhile,
and I believe I am now unable to do any further successful updates.


Questions :
Does anyone know why :
1) update.exe fired up by itself even though i didnt turn on Automatic
Updates?
2) update.exe takes up 100% CPU resources?

Does anyone know how :
I can resolve this problem (set it back to automatic and not hog my
resources? )


THanks.

pinz