I've installed MOO3 in my GOG games file along with my other games, but when I try to run it, I get nothing on the screen. The game icon appears in the task bar, but nothing else happens. Task manager cannot affect the game, end it or do anyhting to it, the only way i can end game is to restart computer...

Does not start for me either and same for Divine Divinity, strange. Both of these games have been installed on my computer for a while and both used to work just fine.

Maybe Microsoft added something to their latest update that targets old games?

Hello,
There has been a change pushed out by Microsoft. I've seen it in a lot of older games where you now have to launch a game multiple times before it actually starts. It was a security update to prevent malicious .exe files.

Is this perhaps the reason?
https://www.gog.com/forum/general/old_games_not_launching_and_eating_100_of_the_cpu_on_windows_7