To enter X920BT testmode:
Turn Power On
While holding home button press: rew, fast, rew, fast, rew, fast (or fast, rew, fast, rew, fast, rew, can't remember right now which one is first).
Screen will go black, so release the home button and wait.
Testmode will be on, with full file copy capabilities.
Tested on mine, works.
Now we just need to know which files to change.
Am I wrong VBLUE42?
Cheers!