Emulation takes alot of CPU cycles. The X-Box simply doesn't have enough power to emulate a computer with that much power. General rule is that if you're emulating one computer on another the one your using must be much more powerful than the one your emulating. A 733mhz X-Box can easily Emulate a 1 mhz NES or 3 Mhz Super NES or a 7 Mhz Genesis, and maybe even a 33mhz PS1 or 93 Mhz N64, but a 300 Mhz PS2 is a little bit much to push.