You cannot install the application outside of the C drive, but you can move your music library out to another drive and have iTunes access it from there.
If your library is consolidated, you simply move the iTunes Media folder to the other drive and then start iTunes while holding down the shift key. It should prompt you to select an iTunes Library, you can the just navigate to the location of the ituneslibrary.itl file in the iTunes media folder you moved.
click here ➜ Move your iTunes library to another computer - Apple Support
If media is strewn about in different folders and not consolidated in the iTunes Media folder then you will need to consolidate it or recreate the folder structure in the other drive.
click here ➜ Make a split library portable - Apple Community