Thanks, all, for the assistance. I found the Dell Datasafe backups DVDs that I had made some time ago. I tried them out, and stopped them before they could restore my computer to its original state (yuck!). I just wanted to test the process before I might REALLY need those DVDs.
The backups restore the computer to its original state, and there is an option to restore it further to its current state.
I've been using Macrium free, and it, too, has a recovery disk, which I also created and tested. It can recover a backup created only in Macrium, though.
I suppose the ISO file, my original quest here, is buried in the Dell Recovery partition.
With the two recovery options, though, I'm satisfied and have stopped trying to find an ISO file on my system.