The problem may be with the wireless adapter in your computer. Check the manufacturer's site for a Win7 driver for the wireless adapter.
Also, have you supplied the correct password and chosen the right wireless security protocol (WPA etc) for the adapter's user interface (or Windows' equivalent).
Suggest you try hooking the computer to router via an ethernet cable and disable wireless security and see if you can connect then (see router manual for how to address router's setup screens via your internet browser).
