Coverting a Stock PC to a new case?

looks to be standard microatx.

go to your respective order website (scan, overclockers, ebay) and find a case that you like. they all come with instructions. genrally the last thing to take out is always the motherboard.
 
I'm not sure if it can really be done or not. The problem with pre built systems is that they use a lot of proprietary hardware that is made for their cases (Dell, Acer, HP are notorious for this). I'm not sure if Asus does that or not, check the layout of the motherboard before you decide to go through with it.