Unlock a Philips portable DVD Player Pet 741/37
It worked for my Philips PET741/37:
1. Power ON the DVD player without a DISC inside
2. Press the skip keys in this order (the keys are under the "disc menu" and "stop"): right, left, right, left, right, right, left (YOU DON'T HAVE TO GO TO SETUP MENU, just do this in the "blue screen".
3. It will show a menu with region, now use the arrow keys to select "region" and change to "test 0" (all regions).
4. Press OK to confirm. Enjoy