If your "Controller panel" key binding is still available (default key is 'c'), simply call it, then with your mouse either click on 'Default Settings' button to reset everything...or 'Launch game/ (Interface) Select' button to map this command only to a new key.
If you don't have access anymore to that panel, go to "C:\Users\"Your User Name"\AppData\Roaming\mGalaxy" folder, then delete the 'Preferences.xml' file.
On mGalaxy start, the controller panel will auto-open and you will be able to do the same as advised upper!