Q: I have a computer with NVIDIA GeForce 8400GS video card and Pentium(R)4 3.00GHz processor , and I cant set Games resolutions higher than 1024x768 and the highest resolution of my monitor is 1280x1024
A: NVIDIA GeForce 8400GS video card is the weakest (intended just for office and simple multimedia use) and this is it's maximum resolution for these games. Buy a more powerfull one like http://www.newegg.com/Product/Product.aspx?Item=N82E16814121087