HELP!!!!!S.O.SSave me PLEASE!!!

OK, I have a new PLextor 708-UF external drive. Its all hooked up, the computer sees it, all of my programs, dvdshrink, nero, clone etc....they all see it. It reads fine, I put in the disk I want to back up and it reads it, but when it goes to burn, the Plextor does not eject, the other HPdvddrive door ejects and I have to put the blank media into that in order for it to burn. I double checked Nero and it clearly shows the new drive, is there something else I have to do? I tried ejecting the plextor myself and putting in the blank, but it won't burn unless I put the blank into the HP. thanks!