If this computer worked fine on a prior OS such as 7 or Vista etc and you just made the upgrade to 8 and are now having this issue, then I would track down drivers for your wireless adapter and hopefully there is a Win 8 driver available, otherwise you will have to take a chance with Windows 7 64 bit wireless driver etc.
Do you know what Wireless NIC your system has? Also what are the hardware specs of your computer, make, model etc?