You mean that has a 15 pin connector, right? That would be for the old gameports that were provided on sound cards. That joystick might have come with a gameport to USB adapter, and you might be able to find one on eBay. Either that, or you can purchase a gameport to USB adapter.
The 9 pin adapter attached to the sidewinder joystick came with a seperate piece. It coverted by attaching the male part to the female 9 hole part which broke off to USB. It came with software.
My wife reorganized my office before Christmas, the small piece that has USB at one end and 9 hole on the other is what Im missing. I am searching for that part also. Ive tried fry's electrocics, E Bay, but they arent out there. Iyiu have any luck let me know.