On XP,
Windows
Update and
Microsoft
Update appear to run completely unthrottled under SVCHOST.EXE.
MU is worse because even when set to "
Notify me but don't..." it compares every MS software component on your PC against the latest update on their server. This routinely took 15 to 20 minutes (Athlon XP 2600+, 1GB RAM) during which time the PC was practically unuseable so I began just killing it using 'Process Explorer', until one time when some files were corrupted and I had to 'System Restore'.
So on home PC, I've reverted to
WU only,
Notify - and periodically manually check for Office 2003 updates. (Though there was an update for Outlook a few days ago - maybe it was a 'priority' or MS have changed the way
WU and
MU are differentiated?)
On work PC (where I'm the only user) updating is fully user-initiated - which reminds me -
I'd better check for updates... 