Buy it for your pc. If you have a pc that is less than 4 years old (Probably any pc from 2004+ will run it perfectly but 4 years old is playing it VERY safe ;]), it will run Morrowind perfectly. It's 17 bucks on amazon and you have THOUSANDS of free mods to boot which add THOUSANDS of hours of gameplay (literally, I have put well over 2000 hours in this game since I started playing it back in 2004). Xbox = lackluster experience. PC = Best game ever made.
In regards to the Xbox 360 question, I seem to recall reading somewhere that Morrowind is now compatible with the 360. Try searching the forums