This post is made just in case someone else has the same problem in the future. This incident was on a Palm m105 with Palm OS 3.5.2, HandyShopper 2.5.1 and PocketMirror 3.1.2.

Due to a comedy (tragedy at the time) of errors on my part, I messed up some HandyShopper database files on my Palm, '*.PDB' files to the Windows OS. When I tried to reinstall backups of these files with the Install tool, I got the error message (from memory) "File already exists in <username> download directory". This made no sense, since nothing was showing up in the Install Tool list of files to install. I will skip a description of my plodding detective work, but I found that HandyShoppers' way of keeping itself updated is to keep it's own Install File list "HSPrefs.PDB", so the trick is to locate and double click on that file, which pops up the Install Tool dialog, and then Remove the conflicting file, but not "HSPrefs.PDB".

Boring, huh?