Yes, there's an Sega CD/32X emulator for Xbox (since the Xbox specs are perfectly like a computer), but I don't remember the name of the emulator.
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May this shed a world of light onto your wishes of the xbox.
http://worldofstuart.excellentconten...xbox/xemus.htm
Yabause gets on average about 4FPS on the DC while running (I have a FPS counter in my debug version). The max it has ever hit was 15.6FPS. Granted, the version released before that only ran about 1/2-1 FPS, but that's besides the point.
There's a lot of room for Yabause to improve on the Dreamcast. Some of which could help eventually with Genesis/Sega CD/32x emulation, but I wouldn't count on anything myself.