My joystick wasn't working in Red Baron 3D. I found some really old threads where other people had the same problem, but I didn't find a solution in any of them. After playing around with windows for a while, I found a solution that works for me. Here is the fix:

Press the Start button.
Press "Devices and Printers" on the right hand menu
Find the joystick you want to use there. Right click it, and select "Game Controller Settings"
Click advanced.
Make sure its selected as the preferred Device.

That was my problem. It was set on "None"

You just fixed my problem. Thank you so much!

Thank you so much! This exact fix solved my problem with RB3D not detecting the joystick (MS SideWinder 3D Pro) at all.