WMI Issue

I need to open a port for Azureus, and trying to specify the port in LAN Properties I get the following message:

http://i38.photobucket.com/albums/e108/boppington2000/Properties.jpg

I first got this message a couple of years ago, soon after I bought this PC, when I was trying to adjust the size of the Windows paging area. Going back to the earliest available restore point didn't fix it, so I just hoped it wouldn't be a major problem.

I'm running XP MCE (fully up-to-date)on a Dell Dimension 5150, and using a SpeedCom wireless ADSL router.

I can't find anything useful on the Microsoft or Dell sites, so any advice as to how I can overcome the problem (short of a full rebuild) would be very gratefully received.

(Oh, and though I doubt this has any bearing on the problem, my Dell came with Norton Antivirus installed, and I removed it using Symantec's online script. Could that have corrupted WMI details? I know Norton tends to get its tendrils in pretty deep!)