Choose "joystick interface"

What do you mean by "I can't disconnect all USB controllers, they're on the motherboard"?

1. Do you mean all your usb controllers are plugged into usb ports on the back of your computer?
In that case you may want to get a hub and velcro it someplace convenient so you can plug and unplug as you wish. Some games get confused when 2 or more controllers are plugged in so the hub approach works for me.

or

2. Do you mean you have a joystick plugged into the back of the computer in the joystick port of the sound card?
In that case, I think you may have a problem. FMS may only want to see the what's plugged into the joystick port.

Now a little variation here. If you fall under category 2 and your joystick is a powered force feedback type using an external power adapter, you MAY want to try unplugging the adapter from the wall. That can sometimes take the controller off line so that the computer won't see it. That's the way it works for my powered usb wheel. I can have the usb port plugged in but if power adapter isn't plugged in, the computer won't see it and older games won't be confused by it.