My nephew bought an X-box in South Korea when he was there for army duty. Anyway he left it here for awhile and I decided to take a look at it. This X-box looks just like our US X-box but is modded and needs a converter to plug into a 120V outlet (Backward US ways

). He bought it this way in SK.
His X-box has Uleash X V.0.37.1218a and the Xbox itself is version 1.1. It also says it has a 120 GB harddrive in it. He has about 20 X-box games stored on the harddrive which was not surprising to me but what did surprise me was that he had what seemed to be a complete library of SNES, NES, and some other older game systems and games\roms that were very handy to choose from the Modchips Operation systems menu, or atleast thats what I'd call it. This must be legal to buy in stores over there since he said he bought the X-box modded and with the games already installed.
My questions are as follows:
How do I find this modchip or even a premodded X-box like his without going to SK?
Can you really use a different harddrive in the X-box?
I'm not real interested in putting X-box games on the harddrive since we already own just about every decent game there is leagally...Well maybe putting some of the most played games on there wouldn't hurt in order to save from having to rebuy the disk when the middles start to crack away from taking them out of the cases all the time, but what I'm really inerested in is putting the old SNES and maybe N64 games on it. I have the rom files to most all the games I own on those old systems. Is that what I'd use or am I completly missing the target here?
Is there a way to back up some of the stuff he has on his X-box? If so how?