Why there is corrupted graphics when I played quest for glory 1 VGA for couple of hours? I get strange colours over the entire game. I remember that even 20 years ago on my old computer sometimes happened the same.

I don't know why it happens, but I do know it's a common bug - everyone gets it.

The only solution is to restart the game.

Yes I know I simply restart the game. That happens only in QFG1 VGA, other games are fine.

Yes, it only happens in QFG1 VGA.
I didn't say otherwise.