If you turn the graphics down pretty low, you might be able to get Gears of War to run on that system. It has to make due with only 512MB on the 360 after all, so it's at least worth a shot.
If someone can suggest a 3rd person shooter game which can run on my computer specs (as given below), I would greatly appreciate that.
Specs:
Intel Duo Core 1.7GHz
RAM: 2.5 GB
No external graphics card installed. (Its built-in intel graphics card)

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