This game simply don't work on Windows 7.
Got a Windows XP Professional VM and it works like a dream.
Is this allowed or is this banned?

As far as I am aware, the discussion of virtual machines has never really been brought up in the community, so I don't believe any decisions have been made. Assuming that all of the other rules for the game are followed, I don't think there would be any issue in submitting a run utilizing a Virtual Machine.
If you want to try to get the game to work on Windows 7+ anyways, id recommend this video:

I can't install the game.
After I put in the serial key, nothing happens.
The installer disappears while the processes do nothing in the background.

If your'e having trouble installing the game, id suggest asking here https://discord.gg/Q4hatx im not the most knowledgeable for this part of the process, but there are plenty of people here who could certainly help. This would also be a better place to get a solid answer on Virtual Machines