[Maanavi]

i recently bought a new htc touch diamond but i can't seem to figure how to change its ringtone from "ring-windows mobile" to one of my songs from my music library. when i go to settings, there are custom ringtones allready installed but there isnt anyway i can change to one of the songs i've added on to my mobile {{ like a song or something}} please tell me how to.[[i would prefer a step by step instruction though]]