Is it possible for a CD to slip off the vertical drive and fall into the drive? I'm using a vertical Dell PC, inserted the disk, but when I opened the drive, the CD wasn't there. Without taking apart the PC, I used a flashlight to see if I could see the CD, and I can't. But, is it possible for the CD to have fallen off the drive and remained inside the secured drive? Another CD was put in and read by the computer with no problems, and the drive continues to open and close.