1. Power on player without a DVD in the tray
2. Open the tray
3. Press 1, 3, 7, 9
4. Wait for the asterisks to go away
5. Press 0
   • A warning should appear
6. Press ENTER

1. The disc tray has to be empty
2. Open the disc tray
3. Enter 8, 8, 8, 0
   • the last digit stands for the region
4. Press ENTER

The first two didn't work for me, however the following did:

1. Turn machine on
2. Press setup
3. Hold on remote fast forward (FF) for about 3 seconds
4. Press fast reverse «
5. A debug screen appears, that doesn't mention the region code. Press zoom on the remote.
6. Pressing zoom pulls up a new debug screen with the region codes. Use the arrows to select 255 for a region code (region free).
7. Press setup to exit the debug mode
8. On the regular debug screen, exit normally. You should know be able to play everything.