UPDATE. after i posted this, i tried to open Photoshop forum and my browser page froze. my whole computer froze. i had to turn off the power and boot again.
i tried again to open ps, with same error message.
I tried a suggestion on the only other thread about this i could find--which suggested resetting preferences : RUN/%appdata% and select adobe folder, but i couldn't get that far because that didn't open anything. it asked what program to use to open it. I can't seem to locate this manually either, by opening the adobe folder.
UPDATE: i saw a suggestion on the web to hold down CTRL ALT SHIFT keys while opening the program. It asked if i wanted to delete my settings, i said yes, and photoshop loaded. Then i went to windows/my workspace and it loaded up my previous workspace. (At some point i think i selected to save my preferences when i reinstalled, or maybe that wouldn't be the case). Anyway, This worked.