To download the drivers, I recommend checking the official website from where you can obtain the latest drivers including the network one. Access the page, then select Windows 8.1 64bit as the operating system and scroll down to the Network category. Expand the category and download the driver for the Ralink brand. Save the package, right click it, select Run as Administrator and follow the instructions. Reboot the computer and you should have the drivers installed for the 64bit version of Windows 8.1 .