This is a tale of two iMac's and two unused leopard install disks and a retail upgrade version of Snow. One for me (iMac) and one for the kids. The HD on mine became corrupted and subsequently unrepairable in using disk utility. I had to erase. Now after many hours of trying to get an OS on the hard drive, I am writing to a forum for the first time in my life. On the Imac gone bad, I have a successful partition with Windows 7 running just fine. I first read the little white book that advised me to use the DVD install disks that came with my computer. I pulled the set out of the white carton and got after it. That was about 10 hours ago. I tried several times to get the install dvd to start working. Each time I received the subject error. So, even though my Snow was an "upgrade" I realized that it would probably work and then I thought maybe it was required because I was running Snow before the crash. I got partially through an OSX install several times (once within 10 minutes remaining allegedly (after waiting for almost 3/4 hour for the 10 minutes go by). Each epic fail required me to erase the HD each time and do the repair and verify function until I received the All is OK message. After trying to reinstall the OSX from Snow several times, I went to the internet. Spotted something on a different forum (mini dell or something) wherein a guy said the only dvd that might work is the actual one that came with the computer but most everyone locates a dvd (with a retail iso) or purchases a retail OS dvd in order to reinstall a OS to a crashed hard drive! What? What? Are you kidding me, to think that the dvd that came with my computer would not install the OS again was to much non-apple. It did start me thinking....I wonder if this computer knows which one of the two original OSX Dvds is the correct one and is it possible that could be the reason my attempt to reinstall Leopard a dozen times failed? Say it ain't so Joe! As I type this, I'm staring at my screen (I'm using the kid's Mac) and it says 97% percent complete in checking the DV consistency (?) on the first attempt using the 'other" dvd (must have been the one that came with it). Both DVD's of course are identical in appearance but looks are deceiving. Up to 99% complete, saying a prayer now... YES, it is now moving into the actual installation phase of the installation process. What a nightmare. My question is, should I now attempt to upgrade the OSX again with my Snow retail dvd OS software? What if it fails? It should work now that the original OSX is going to be on the HD, right?? Obviously, I am hoping a real expert answers this..