I tried to install from the ISO file in windows 7 64 bit and the setup was not even starting. I could see the setup program running in Task manager but it was doing nothing. The problem is common with older games in Windows 7 that by default run Microsoft Game Explorer. Microsoft has stopped the operation of the servers of game explorer and this causes the problems.
A simple but not permanent solution for the setup to work by following these steps :
1) close setup in Task manager if it is already running ("End process" button)
2) close rundll32 in task manager (same button)
3) run setup again (to make sure it would succeed I chose compatibility with Windows XP and gave Administration rights, but I don't believe it is necessary in windows 7 - maybe it is in windows 10)
After these steps the installation proceeded normally and I installed the game in a different folder (not under Program Files (x86)). If the game doesn't start try to rename Enigma.exe file to something else, e.g. Enigma1.exe and use this to start the game. This worked for me and I hope it will for those who still want to play this game (I personally don't play it but I tried to install it for an old friend).
For a more effective method (but requires changes in windows registry changes) see
https://www.gog.com/forum/general/ol...indows_7/page1