How could it be monitor settings when ONLY his movies became bright with his new GPU?
Yeah, I had the same problem with those 77.72 drivers.
Anyway, here is a fix in a bit more detail:
start -> control panel -> display -> settings tab -> advanced -> your GPU tab -> color correction slideout
Change the "Apply color changes to:" drop down to "overlay".
You should know see a curve of some kind. What you want to see is a y=x line so you have an even spread of color effects. Any sort of curve will exaggerate brightness or darkness.
In order to make it a line, change the "color profile" drop down from "standard mode" to "advanced mode". This should make it linear or at least give you the ability to change the line yourself. If worse comes to worse, you can change it and make it a line yourself, though I don't think it should come to that IF you do it properly.