Games won't play - hear audio but see only desktop

I am having an infuriating problem. I am trying to play some games on my PC (ones I haven't played before) and I am getting the same problem with about 50% of them. They are not new games which outdo the capabilities of my graphics card.

I load the game .exe and it starts up and I can hear the opening music but it jumps straight from the initial black screen just as it loads to a view of my desktop. The PC thinks the game is running (alt tab shows this and the taskbar icon is highlighted).

I am running windows 7. I just reverted from windows 10 and am wondering if Microsoft is somehow punishing me.

I've tried googling for this problem but can't find any hits in the ways I've tried to express it.

Thanks in advance for your help!