For my Mac Pro 2006 1,1, I purchased from Apple the Snow Leopard OS on CD a few years ago. I bought a new iMac in the meantime and never upgraded the Mac Pro. The Mac Pro is now working with Leopard. Today I want to do that but I foresee a problem. The disk drive #1 on top isn't showing the disks on the desktop once installed into the drive and the drive closes. Therefore, I am not certain that those CDs are either too old (PC/MAC games) or if the drive itself is still working. It operates smoothly and closes completely so its mechanics are not a problem. If it comes down to it, how can I put the CD onto a thumb drive to install Snow Leopard that way? I would have to perform that operation on the iMac. It helps me to have a workaround if the worst happens and I've never done this before. Or, how do I start the Mac Pro from the CD if that is even something to be considered. I'm kind of shooting in the dark here as my knowledge is not up to speed for these possibilities should they occur.