Help with a friends build

[SuxoR]

Hey guys I am looking to build a computer for a friend and need some help on a build.
He wants to be able to play Modern Warfare 2 and Dragon Age:Origins on good settings (not max but look and run great)

He'll be getting a monitor later on (including keyboard and mouse) but I believe he needs the OS
Can you guys help me out with a decent build?

Thanks in advance!

 

[Ste]

How much can he spend?

I would recommend at least a 800 or 900 USD budget, but more is better.