I'm trying to watch some of the DVD Backups that I created on my PC with DVD Shrink and the discs won't mount to the desktop. Of course, nothing will play it since it's not mounted. I thought it might be a disc type problem, but I have tried ones on DVD+R and DVD-R and none of them mount. They ALL show up in the Disk Utility and it reads the correct disc type and the volume name. Why won't it mount - can anyone help?!