Xbox games can be played on a PC through use of an emulator program. Emulators enable a computer to function just like a regular console system, though there are several steps involved with setting up the emulator on the PC.
Download an emulator, and set it up according to the instructions included. This may require downloading additional computer files called BIOS, which allow the computer to function as an emulator. The next step is to download ROMs, or games, and run them using the emulator. Emulation is legal in the United States, but it is illegal to download games under the Berne Convention, unless the copyright for the game has been released.