I may have had an ahah, but I want to check it out with this group first.
See entry number #27232 - 11/01/13 01:27 PM in a previous thread named "Re: I've had it with Mavericks. How do I revert?" where I described how I got rid of Mavericks and reinstalled Mountain Lion and its files. There, I was dealing with two systems that had no installation DVDs. Until now, I've blocked that successful adventure out of my mind because i've been dead set on using the Snow Leopard installation disk. That may have been self-defeating.
I currently have a complete backup of Snow Leopard on an external hard drive that was made just before upgrading my wife's computer to Mountain Lion. Before the upgrade, I turned off the external drive so as not to clutter Time Machine with garbage as we installed Mountain Lion. This was done because the iMac was acting very weirdly with strange visual aberrations on the screen. We've now discovered that a wireless telephone sitting next to the iMac was causing the problems. Things cleared up when my wife moved the phone to another room. Before that discovery, we upgraded her iMac to Mountain Lion in case Snow Leopard was having a problem with some new software.
