I have noticed a minor difference in behaviour between Windows XP
SP1 and SP2 wrt WindowsUpdate V5.
If you configure the Internet Zone to High security, then visit
WindowsUpdate, you see a page that advises you to add the following
URLs to the Trusted Web Sites list box:
http://*.windowsupdate.microsoft.com
http://*.windowsupdate.com
This works OK for a system running XP Pro SP1 with all updates, and
you get through to WindowsUpdate after following the instructions.
But on an XP Pro SP2 system you simply get the same page back.
These settings work OK for both SP1 and SP2:
http://*.microsoft.com
http://*.windowsupdate.com
(Haven't tried any others BTW)