The MkIV from a 2004 745i will not work in the X5. The 745i uses the optical MOST bus, whereas the X5 uses the electrical i-bus. Not compatible and not interchangable.
A MkIV from a e38, e39, e46, X3 or X5 will work as long as it is from a vehicle with a color screen (versus the monchrome screen found in certain e46's).