It is unlikely to be the computer. Unless you have something unusual, most operating systems have drivers for wireless cards. Does the computer recognise the router? Is your router set up properly? Are you putting the right key in the computer to communicate with the router?
It this a laptop?in which case you can become a road knight and slowly drive down the street until your lappy picks up a signal from one of the houses. Then you'll know if it is your computer or the router.