What games are suitable for my pc.?

I have a 2.7 gz AMD Athlon Processor, Nvidia 9400 graphics card with 1.1g memory, 4 gigs of RAM, Windows 7. Most games work good, but fallout 3 is laggy when im in houses for some reason. Could someone either help me if Modern Warfare 2 will work good on my computer along with my primary question? Thank you.