Gears of war for windows again!?

Now I am getting mad! I got a new graphics card of Nvidia GeForce 7100 GS and even called customer support and talked on the phone for two hours! It is still lagging beyond comprehension. The game plays, it is accessible, and all that, but it doesn't not run efficiently well enough to be played. The lagging is just maddness. Help? All I want to do is just play some GOW. Is that too much to ask?