Photoshop 19 api-ms-win-core-synch-l1-1-0.dll missing

Running Photoshop 19 on a windows 8.1 64 bit system. Everything was fine until a couple of days ago. Now Photoshop fails to initialize. Most of the time it says  missing api-ms-win-core-synch-l1-1-0.dll. That will pop up a few times then then pop up a message saying "could not initialize Photoshop due to a disk error."  Sometimes it just goes right to  the could not initialize error.  I have checked and I do have the  supposedly missing dll (in both windows folders where it belongs.) I had updated an unrelated program shortly before my Photoshop problems started, so I unstalled that and did a system restore to bring Windows back to a point where everything was working. That didn't help. I have uninstalled and reinstalled Photoshop probably a dozen times now (still version 19 because I can't upgrade any further on this version of Windows.)  Now I do have an old copy of Photoshop Elements that runs just fine, and all my other Creative Cloud Apps run. (Lightroom, etc - I have the photography plan.) I have scanned my harddrive for errors, I have defragged it, I have run CC Cleaner to get rid of any junk that ws hanging around.  I have plenty of free space on my hard drive, and ther only program that is giving me issues is Photoshop.  I have toyed with the ida of getting rid of the entire Creative Cloud suite and reinstalling, but I'm afraid I might break something else. I have also toyed with the idea of updating to Windows 10, but that seems like that would be a bigger hassel that could potentially break more things.  I could use some more ideas on what to try.... Googling has not helped me much.