How can I turn my PC Joystick into a controller? Such as for SNES, GBA, etc?

The joystick is a Saitek ST290 Pro: http://static.productreview.com.au/pr.products/59608_saitek_st290_pro_joystick.jpg

I don't need to retain all of the buttons, it doesn't matter to me. I'll probably wait awhile, then bust this thing open myself and go crazy :D

Thanks for any help in advance!