Try trouble-shooting by right clicking on the network status icon and clicking troubleshoot problems.
If that doesn't solve it if you have the disc that came with it install the drivers if you already have, in the start menu search device manager then click on device manager then go to network adapters and find your wireless card and uninstall it by either deleting it (press 'del' after selecting it) or right click and uninstall then click ok or yes when prompted and restart.