Small Desktop for COD4/COD5

[escapedturkey]

I'm going to Europe for awhile (I can run my business form anywhere with 
an Internet connection) and I want to setup a desktop that I can take 
with me on an airplane (like one of those Shuttle cases). I'm currently 
in the USA.

Any suggestions what system configuration to get to run COD4/COD5 -- 
cpu/gpu/memory -- with a mini case (like those Shuttle brands). Also, 
suggestions on where to buy the parts, please.

Budget is around $600 for a desktop (I can get the monitor in Europe). 
It doesn't have to be any super system, just enough to run COD4/COD5 at 
60 FPS with shadows on.

Thank you. :)