Microsoft Update on XP SP2 stops working after GDI Detection Tool is run

Hi

My Windows XP SP2 installation was working until I ran the GDI
Detection Tool. Now if I try to access the Microsoft Update page IE
freezes (not the whole PC) before the text of the page displays - so I
assume also before it has started looking for updates. Any other
Internet page displays perfectly and I'm on cable so speed isn't an
idssue. I know (now) that SP2 doesn't need the GDI Detection Tool
(silly me not to read the small print beforehand...). Is this problem
likely to have been caused by running the detection tool? I don't have
System Restore running, so can't roll back. Would it help reinstalling
SP2, or do I have to reinstall Windows? Can I edit any entries in the
Registry (which I didn't back up before starting...) I don't think its
malware related as I have F-Prot and AVG (updated daily) for antivirus,
Adaware for spyware, am accessing the Internet through a router and
that combination has worked for over 3 years.

Thanks for any help.

Sandy