If you are faced with a machine that will dial up and go through the motions of connecting to the Internet but will not load any websites, will not allow you to connect to AIM/MSN/ICQ, will not connect to jacksquat, go into control panel and check Internet Properties. See if it's trying to use a proxy server whose domain goes something like "marketscore.com."
Here's what the damn thing is, and how to get rid of it.
Here's what the damn thing is, and how to get rid of it.