You have cable internet, right? If you have a router, it would be used to connect several computers on one network. You should also find out what kind of modem you have. The reason is this: modems and routers can have built in firewalls, and if you can't figure out which ones you have, you can't fix the problem (if there is a problem).

Some ISPs can make it difficult to connect, especially during peak usage hours. If you could find out which ISP you have, that could be useful also.

Are there any boxlike looking things connected to your computer that you don't know what they are?