Click launch, loading circle appears for several seconds and then nothing happens.

I've tried the following:

Tested every compatibility mode and option (administrator)
Updated and installed DX legacy versions (per GOG support website)
Added game to anti virus exception list
Switched DEP to windows essentials only

Am i missing something ?

System:
Windows 10 64bit
i7-6700HQ 2.60Ghz
16GB RAM
GTX 1070

I'm having the same problem :/

I have the same problem.

Try going with Windows explorer to the folder where you installed the game and run the "Launch SimCity 3000 Unlimited" link there. If that still does not launch the game, enter the "Apps" folder that is there and run "SC3U.exe". If that still does not launch the game, contact GOG support.

Tried both files; they didn't work. I guess this won't get solved without contacting GOG support as you suggested as last course of action.

Windows has a new data execution prevention protocol that blocks a lot of games the first time they are launched. I have to on a number of games launch the game a second time for it to work.

I launched it a second, third and a fourth time and it did not start. I have a question: doesn´t this forum possess administrators or employees of GOG, monitoring the discussion?

Intermittent.

They do have a game technical issue site that can be accessed from Support

I have a solution, that worked for me. I copied the game folder (i will write a detailed description later) on another hard disk. Hard disk D: for example. Then i deinstalled the game folder on the former hard disk and imported the new folder into the GoG Galaxy application. The folder was imported, the game was updated. Then I could start SC 3000 without problems.

Oh right, installing things to Program Files.

Since it became a protected folder, a dumb idea.

What do you mean?
Maybe i can help you.

Basically, Windows made the Program Files folder a protected place; meaning that to cut to the chase, the way many old games work no longer work in that folder.

Okay. I thought, that the most compatibility issues resulted from the former copy protection. There were some significant cases. But GoG makes the most games running through special patchses. But sometimes you have to use tricks.

I feel there's something of a communication breakdown; I was iterating on my idea as to why I think they were having problems.

The issues of WIndows are of no lot of mine.

you are a god, thank you