your not going to be able to play any of those games on this system, It is not worth upgrading one part of the system because the other components will just bottleneck and you will not see very much difference in game play, he just needs a new system all together. I suggest building one, and if you need any help just post on here and we can help pick you out some parts.
with a budget like that, the only notable thing you can do is get an APU llano chip(unless your friend is willing to wait for trinity, then that would be a good alternative because trinity does have performance gains vs llano)
you will need a legit windows copy in order to reupdate your windows to work on the new cpu and motherboard if you take that route. if you bought a retail copy, then it will work. if you bought it from an oem or bought an oem disc to save money during first construction, you will need to buy a new windows disk.