What it does, is turning off all the extra fancy stuff in Windows which creates the effects on your desktop and for example the nice transparent toolbar. WDDM still runs, it just does not show any effects, thus clearing all the memory used to run it, thus clearing extra memory to make games & software run better on poor graphic cards. Try it, really, works great for getting a bit more oomph.
I got a poor x3100 graphic card, which makes programs like Photoshop, Illustrator, autoCAD, etc run pretty slow. By turning off all the fancy stuff it just runs smooth as can be. I just cleared enough memory to make it run great. ;) -- 9xx SOLDIERS SANS FRONTIERS
