yes it is possible because the Xbox is just a PC in itself. There are much more powerful pc's out there than what is in an Xbox360.
The 360 contains 3 single core processors clocking 3.2Ghz each. That is solely for gaming. Some gaming comps use higher Ghz(say 3.6+ dual core). Comps have more hardware in them but the 3 processors are to prevent lag on the memory hog games that are coming onto the market with better than ever graphics. So yes, pc's are faster than an Xbox if you want to make it that way(same stuff

).
Don't know about the 360, but some people have put Linux on an Xbox

.