Hi there,
It could be a conflict with your graphics driver. Before you start updating those, though, you can try changing the renderer used in each game.
In ADWD1, you can press shift + G in game to change the renderer. Try each one, and restart the game between changes.
In ADWD2, you can find it in the preferences menu. Once again, you will need to restart the game between changes.
After that, my suggestion would be to update your graphics drivers, and if you're playing on a laptop, make sure it's on "high performance" mode rather than battery saver.