there kinda like the ol dreamcast disks...they have a special ring o data thats only readable to the xbox and select DVD players...
on top of that the games are SPECIFICALLY programmed for the proprietary hardware in the XBOX. Its not just "Some PC", its optimzed and configured such that the games are compiled to run SPECIFICALLY on the XBOX.
Now the interesting thing is the xbox dev kit runs off a normal PC. You can develop and play on the pc and adapt certain code to the pc. Can you burn TRUE xbox games with your comp? chances are nope...but could you play them??? well all signs point to yes...but how?

I say its possible its just nothings out there yet cause the EULA with microsoft for the dev kit is so ironclad that if u were to develope an emulator from it you'd be reemed by their attorney's. They seem to only want to give dev kits out to certain countries and companies too...ones that are sympathetic to microsoft. The Xbox is probobly one of microsofts most closely held devices as i have ever seen.
I say just splurge and buy an xbox, if anything you have a game center and entertainment center all in one. And on top of that you get decent controllers as opposed to trying to configure some controller to work on the pc....