You have to be sure you created the right type of registry key.
It needs to be of the type 'DWORD' (right-click on the right hand pane, click New > DWORD (32-bit) Value)
I think I managed to copy all the joystick-related entries:
Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\Volition\WingCommanderSaga]
"CurrentJoystick"=dword:00000000
"EnableJoystickFF"=dword:00000000
"EnableHitEffect"=dword:00000000
Copy all of that and paste it into a Notepad window, then hit file > save as and type in "WCS joystick.reg" and set the "Save as type" (under the filename box) to "All Files (*.*)", then click save.
Now, find the file and double-click it to add it to your registry.