How can you use MP3 as a ringtone on the Motorola RAZR VE20?

I just bought a RAZR VE20 and have been trying to do everything to get a mp3 as my ringtone.

I downloaded some music (mp3) to it to the "music" folder on my memory card, I am able to listen to that music, but when I go to Menu > Settings/Tools > Settings > Sounds > Ringer Type > Voice Calls > With Caller ID > External Memory .... it appear as if there isn't any file.

But if i go to Menu > Settings/Tools > Tools > File Administrator ... I am actually able to see all my music stored on the memory card.

Please if someone can help me, let me know
Thanks

Marco