Instructions
Go to the "SIXAXIS Driver Download Site" (see Resources), and download the ".rar" SIXAXIS driver file. Find this file in your "Downloads" folder after the download has completed, and unzip the ".rar" to find the "ps3sixaxis_en.exe" file. Move this file to your desktop.
Plug the Mini-B end of your PS3 controller cable into the port on top of your PS3 controller.
Plug the USB end of your PS3 controller cable into an available USB port on your computer.
Double-click the "ps3sixaxis_en.exe" file on your desktop to launch the driver. Press the "PS" button in the middle of your controller. Your computer will now recognize the PS3 controller.