Cannot install known safe programme...

This is the same one I downloaded? SETUP.exe? Are you running Windows Home or Pro?

Baffling. We both have exactly the same settings, using the same file, unblocked the file, and we get different results. How is your UAC set?



Not suggesting you turn it all the way off like me, just want to see what you have.

I'm assuming you have Admin privileges and are signed on with an account that does have Admin. Probably won't help, but try right click the setup.exe and Run as Admin.... see if you get the same.

Also, I'm looking for any Group Policy entry that may override the Settings we both have and cause this. No luck there so far.

You said you disabled Bitdefender. Verify that it is not running at all, even if you need to disable it completely and do a restart. That's the one big difference between you and me. I don't have Bitdefender.

rafikiphoto said:

Yes, I had been doing that as a matter of course. However, I have been doing a search of the exact error message I have been seeing and I came across this solution on Reddit:
Can't install program on Windows 10 "Your security settings do not allow this application to be installed on your computer" : techsupport
After backing up my registry I followed the instructions and it worked. I got the same error box but with the options you saw. Clicking 'install' I got a 'run' box and the programme installed.

I very much appreciate the time you have spent helping me. Thank you.

Great! Good job finding a solution. And you are quite welcome.

rafikiphoto said:

It would be interesting to know your registry settings for those keys when you get the time.

For that Registry key sequence:

HKLM\SOFTWARE\MICROSOFT.NETFramework\Security\TrustManager​\PromptingLevel\Inte​rnet

I don't even have the sub-key TrustManager.