Dual boot windows 7 ultimate 64 bit and windows 8.1 pro x64 activation problem.

I downloaded both the windows 7 and windows 8.1 installers from https://games4theworld.org/downloads/
I first installed windows 7. I've been using it for quite a number of years and there's a game that I needed to use windows 8.1 on so I installed it on a different partition so I could dual boot. The installation worked fine and windows 8.1 was activated. But the problem started when I tried going back to windows 7. Suddenly windows 7 got deactivated and I got the non-genuine warning. So I used the windows 7 activator. When I booted back to windows 7, it was activated again. But the next problem came out when I tried booting to windows 8.1. It won't let me back into windows 8.1. It just restarts whenever I chose 8.1.

Then I thought that maybe the problem was because I didn't use the activator for 8.1, so I reformatted the windows 8.1 partition, did a fresh install and used the crack that came with it. then I tried booting to windows 7, and it said that it's not genuine again, so I used the activator again, then booted back to windows 7 and it's activated again. Then I tried to go back to windows 8.1, but I'm back to square one because it won't boot into windows 8.1 again.

I'm at the end of my rope. I don't know what to do anymore. I don't want to reformat my windows 7 because it's already got too much stuff on it and I don't want to loose it. Is there a way to make these 2 OS work?