Hello experts I just got a PX 755A. When I burn about two GIGS to a blank disc, it will not let me add files to the disc. When adding, it wants me to insert the disc and. of course. it is inserted. So I tried a DVD-RW. when I go to add files to it , I am told that it is going to ERASE what has been burned on the disc. The "Read Only box is NOT checked.