If you have the security code then it might be worth trying to "reboot" it ( Remove fuse(or battery connection) for a couple of minutes , replace then enter the security code.
If that doesn`t do it, then you`ll have to remove the unit from the dashboard (using special extractors...available on Ebay) and open up the casing to remove the CD.
note: If this unit was purchased "New" then you should return it to the Seller for a replacement or your money back.
RegWorts, May 2008