First of all, talk to the other people in your house and see if they changed the tcp/ip settings for the router through their computer. There's probably a list of allowed devices, yours might have been accidentally removed. If that's not the case, here's some steps. First off, just curious, do you see a connection to the wireless network? Not the actual internet, just to your house's network.
Step one is powercycling the modem and router (or the gateway if it's an all-in-one unit). Leave it unplugged (the power, not the ethernet) for about 20 seconds, then plug it back in.
That will fix it like 80% of the time (I work in a cable internet call center).
If it's still not working, Check your network connections panel and verify that your wireless connection shows as 'enabled'. If not, obviously, enable it.
Still no? Restart your computer. Still no? I'll check back later, there's more steps than are worth typing out at the moment.
