You'll be much better off re-installing CS5 from scratch, then applying all necessary updates manually, since the CS5 Adobe Auto Updater was and remains pretty useless. The hapless updater team in India only began to get their act together on CS6, then fell back into their legendary incompetence with CC and CC2014.
It's a bit tedious, I know. But this will guarantee that you have a fresh and complete CS5 install. Yoy cannot be sure there's only the one file missing, other files could be missing or damaged as well.
Hey, I suspected that was going to be the correct action to take but I think I needed someone else to look at it and tell me so. I will take that on as a post-Santa Claus task!
I appreciate you taking the time to stop by and reply to my post. Merry Christmas.
Jim n' Jawga
You could try a REPAIR in the usual way from the WIndows Add Programs Control Panel (be sure NOT to uninstall, just repair).
Thanks so much for the suggestion. Interesting thing... I went to Programs and Features from my Control Panel.
Photoshop is not listed at all in the installed programs list! Not 'A' for Adobe or 'P" for Photoshop.
I find that to be strange. I wonder if others have the same experience in the installed programs listing. Not
sure what I can do at this time.