Solution worked: PowerISO generates Phantom Drive Letter
All of a sudden a new CD ROM Drive appeared in the "Computer" folder. It was driving me crazy, because scripts were assuming access to that drive letter which was no longer what it was.
I found the problem and right after - found this thread! The slight hint was, the CD color of the icon was gold, matching that of PowerISO.
Function IS useful in PowerISO - mount an ISO image in situ without burning or unpacking.