Adapter
I didn't have a 15 pin game port on my computer either. I assume you do have USB ports. You can buy adapters at many different places but go to Radio Shack and buy a game port to USB adapter for about $16. Take the controller with you to be sure but my G2 controller also had a game port/15 pin plug. There are 4 settings on the adapter but set it on #4.
I had a link to detailed instructions how to properly install it but that link doesn't work anymore. But, it's not hard. If you're running Win XP when you plug the game controller into your puter, XP will recognize the USB adapter not not the game controller. This is correct.
Good Luck