I don't believe you can. Someone may correct me here, but I thought the hard limit was at 5 changes. You can replace the drive, or have an authorized dealer restore it, you can try playing dvd video in VLC media player, or you can use DVDFab Passkey or AnyDVD in the background to remove region restrictions (neither of those programs are free).
DVD43 works in a similar fashion to AnyDVD or Passkey and is free, but not updated as often. http://www.dvd43.com/
There are region free firmwares for many drives, but some laptop drives, like the Matshita drives can't be made region free. We'd have to know the make and model drive.