Do you still have he manual from the time you bought the unit? That would be your first source of referrence to look to. If you don’t have it anymore your left with calling Sony support and getting more help on it or order a manual to help you with the settings. Try this link to see if this will help
http://www.retrevo.com/support/Sony-RDR-GXD455-DVD-Players-manual/id/3115bh036/t/2/
But in the also one shouldn’t forget to do a online search there are a wealth of information for the reading and browsing as well as check the manufacture site for help.