Okay, heres a stumper. Started to work on a PC that the owner could not get to surf the World Wide Web. He could go to his homepage but no place else. I figured it was cached and stuck in Park. Did a scan and found several bad guys lurking. The owner balked at prolonged cleaning and decided to have a factory restore of XP from the recovery partition. Forty-five minutes later we had a squeaky clean machine that still would not venture much past the home page. I could get it to go to google.com and other short domain names such as red.com but any place that had a substantial name such as weatherunderground.com or comcast.net was a no go. He was using a wireless USB adapter for connection to a Netgear cable modem/WiFi router so we traded the adapter out for a known good one from another tower in his home. No change. Even installed Firefox to replace IE7. No change. The integrated network controller was not being used but I uninstalled/installed the driver in case the device was somehow involved with the IP stack. Still no change.
There are two other towers connected to the cable modem/WiFi router, one by cable, the other by USB WiFi adapter. Neither exhibits this problem. Rebooting the modem didnt help either. Checked Security/Privacy/Content controls of IE and found nothing out of the ordinary. Parental Controls and Content Advisor are both off. All temp files, history, cookies, and forms were deleted. Again, no change. At present there are no firewalls, anti-spyware, or antivirus apps installed.