Changed from vista to xp operating systems. downloaded itunes and is saying not a win32 compatible program

I changed my operating system to XP from Vista. I have attempted to download itunes and it keeps coming up with error message. not win32 program. i cant find a shortcut anywhere and its telling me to uninstall all the files and reinstall but i dont even see itunes under the program list. i see it in the old user accounts file in "my computer" but they were all on the old operating system. im confused!