Windows XP users can add a Vista style menu on their desktop using the free Vista Start Menu Emulator, a standalone program that has the same look-n-feel and some common features as the default Vista Start button.Vista Start Menu Emulator won't replace you existing XP Start Menu but place a Vista style wheel atop your Start Button. Or you can drag the Vista wheel on the right side of the task bar and have access to both menu styles.
Vista Start Menu Emulator Requires .Net framework 2.0
http://vseproject.extra.hu/