nVidia GeForce GT620M and Intel HD 4000 combi: Nvidia not showing up

Running Win8 Pro 64bit on a Samsung Series 5 530U4C and it has a built in
Intel HD-4000 graphics adapter and an
Nvidia GeForce GT620M "external" graphics adapter with 1GB of RAM.

Both graphics adapters show up in control panel and both have their control
centers.
BUT DXDIAG will only show the intel HD adapter, and when attempting to play
an elderly game (RageRalley and Midnight GT) i am ask to select the
DirectDraw driver and it will only show me the intel hd 4000 and NOT the
nVidia one.

I do know that this is some kind of combination between the 2 cards, i also
know that notebooks are not really for gaming and also i know that Win8 is
not made for running old games.
(the mentioned games hence do not run properly)

Still the interesting question remains: in such notebooks with combined
graphics cards, is there some way to select the better external card as the
main preferred card and to prevent the intel hd 4000 from being used?

greetings

Roland Schweiger