I have bought a secondhand car with a CDX-M800 compact disc player but the previous owner doesn't have the code to release and allow it to be played. Can you help?

I tried to find a code for your stereo at Sony but tech support is closed right now.I am providing the link to them and you will have to contact them.These lockout codes are a real issue but I don't think it will deter thieves.They should give you the code for free.Also,if your battery ever gets disconnected it will lock up again so write down the code.Good luck! Greg
http://esupport.sony.com/US/perl/contact-land.pl

Hello,

You will need to get the papers that came with your car, search all the documents that came with the car, the code to reset your car radio is written on one of the documents that came with your car. If you cannot get it, you will need to get the serial number on your radio and contact the dealer for the reset code, because, the dealers have the reset code, but you will need to tender prove of ownership before this can be done.

Can you provide me the serial number of your car radio,maybe i can suggest a code that may work.

Take care.