i really dont think its anything to worry about. A box thats vulnerable to a five year old worm will not survive long on the internet. these machines are usually in the hands of users and not professional administrators. if you go to that site you'll usually see under construction or some shabby attempt at a web page. my guess would be its a recent re-install where the user included iis4/5 and didn't bother (for lack of knowledge) to patch.

in the past ive written to ISPs, tried to contact the owner of the computer or left notes in their all user\start-up folder explaining what was going on but like i said their operating on borrowed time.