OK. Done that. No change.

Do I need to reboot after making the change? What does it do exactly?
Edit Actually there is a change. Windows won't now let me change the processor by right-clicking the exe:
Let's see if enabling desktop composition restores things ...

(I've looked it up by the way and am not really any the wiser).
Edit2 Nope. Things are screwed now. Perhaps a reboot will do the trick? [This is why I don't usually mess with driver updates etc. You fiddle around for hours trying different settings of various things, and the net result is usually a loss of something that worked before with the original problem still intact. Oh well.

]
Edit3 This is getting weirder. I can still change the GFX processor when I run my DBPro exes but not for this particular game.

I guess I'll just have to run it with integrated graphics set as the default. A pain since I would prefer the NVidia GFX to be the default.