Several years ago, using a game pad on a PC was a tangled mess of driver installations and serial cables. With the arrival of USB and plug-and-play compatibility, using a "controller" with a PC is just a matter of plugging the controller into the appropriate port and configuring your buttons in the operating system.
Plug the game pad into the appropriate port on the PC. Make sure it is plugged in firmly.
Listen for the operating system (OS) to make a system sound, acknowledging that the game pad is connected. Wait for the OS to install the proper drivers.
If the controller came with software of any kind, place the disk in your optical drive and follow the on-screen prompts to install. Launch the newly installed software and find the "options" or "configuration" tab. Set the correct bindings for each button.
If there is no dedicated software, launch the "game pad" control panel or preference pane. In Microsoft Windows XP, it is located in the "joysticks" section. In Windows Vista and 7, it is located in the "hardware" section. Click the "configuration" tab. Click on each binding and assign a game pad button to each one.
Test your button assignments in the control panel window to make sure that they are all functioning properly.
Within your game or application, launch the "options" menu and configure your controller's buttons for that specific application.
Pay special attention to the diagonal bindings, as they can often bind incorrectly.