It will help to know the Windows 7 computer model or specs and the GPU model installed on it.
Where you able to find and install the drivers for that GPU on the Windows 7 PC?
Since Windows 7 is not getting any updates and support, I would not mess with one that's working.
You could easy explain that at the time when that PC was released it was not made for that task.
It's like trying to go off-road on a Toyota Prius.