For a first step, I'd check that your wireless adapter is running correctly. You can access this via the Control Panel > System > Device Manager (on the left) for windows 7. Find the "network adapters" on the list and expand that selection and you should see your wireless adapter. Right click that adapter and select "properties"
If it states that the device is disabled in the device status box then there should be an "enable device" option, and if there is a problem with the driver for that device then the device status box will reveal that also.