sucks bro.
Don't know what to say.
perhaps if you actually told us what happens when you try to run a game and maybe your system specs that would help us know what we are up against.
I assume you installedl the necessary drivers for your GPU along with DirectX and Visual C++ Redistributable packages as well as Windows updates.
Also, why roll back to W7 from 8.1 with a fresh install? Makes no sense. Why not W10?