I use my laptop to play as well and I have a Mobility Radeon 4550HD, as well as an Intel chip which comes on i3.
What I do is set my Rad to be the main card, I've set up that it will only work if lap is plugged and just that.

When I open the game, it just shows the Rad, never shows the intel. Try just right-click your desktop and pick change graphic card option, will be a lozenge-like icon, half blue, half red. That normally works for me.