Ok. When I select "Microsoft Sidewinder Precision Pro (USB)" in your launcher, it sets the value to 0.
When I set it to "No Joystick" it sets the value to 99999
After selecting my joystick, if I go to the retail launcher, it says "" in the current joystick box.
If I pick my joystick from the retail launcher and then go back to your launcher and view the registry, it says the value is 1 and "No Joystick" is selected in the joystick tab.
Despite this, a value of 0 or 1 still produces no joystick action from within the game under SCP.
Oh, also, on my desktop (where it works), the registry value is 0 for both retail and SCP.
Hope that helps.