Okay, I'm on Windows 7 and the only product I'm currently interested in is Photoshop CC.2018.
I am on a 64 bit machine, AMD processor. Tons of memory and GPU power.
First move as a total N00b...follow instructions. Uninstall Photoshop and reinstall photoshop.
Error 16.
Second move: Run as Administrator. Hey, it worked! For one day.
Woke up today: Error 16
Found instructions to fix permissions and change search option on this site. I have done that, probably 10 times now. It doesn't work. Yes, I've rebooted.
Did a run of your "Obliterate all Adobe software" utility and reinstalled after that, didn't work.
Enabled Guest Account, restored "Everyone" to relevant folders.
Error 16.
I contacted chat support from Adobe and let them have their way with my computer, and watched them for 2 hours do everything I already did, and a whole lot slower. When they asked me to reboot, I did, and they were gone, no way to get them back evidently with the software they put on the computer.
Tried to log back in to support in the link given in the email to me, and it sent me on a "enter your password" endless loop.
So now you know everything I've been through. I am BEGGING YOU, I implore you...do not address me like a n00b or like you're following a script. I swear, I will absolutely lose it. Please read what I wrote about what I did and don't ask me redundant questions. Your usual responses do not work for whatever reason.
Please just make your product work properly and tell me how to get back to what I need to do with it.