Wayne, would it work to rename photoshop exe in your backup drive? You could rename it back if you should need it. Just wondering.
I'm on a mac. yes I can do things to force LR to use the correct copy of Photoshop. I can unmount the drives, delete the other copy of PS, probably zip them as Jeff suggested. However, my system is set up so my boot drive contains OS and applications and is a high speed PCI based SSD drive. I use carbon copy cloner as my main backup program, and every night this entire volume is cloned to an internal raid (raid 0). This raid is actually cloned once a week to an external raid 5. These are automatic, run quickly because only changes are updated and not much changes on those volumes.
Nothing I do can gets LR to use the correct copy of Photoshop as it's default. I can unmount the volume, delete the preference file, relaunch Lightroom and it works. however, if I quit Lightroom, remount the backup volume (which happens automatically each night) it will go back to the wrong copy.
I'm pretty baffled. I may have to uninstall all Adobe apps, run the backups so they are uninstalled, reinstall the apps, launch LR while the only copy that exists of Photoshop is the correct one, then see what happens after Photoshop and LR are backed up to the other two drives.
Very odd, it just seems logical that it would always look in the same directory for Photoshop, not on some other drive in some other folder somewhere.