MP3 Ringtone on SMT5600
I’ve seen a lot of answers to this question, but here’s the one that works.
If you want to use a custom ringtone on the SMT5600 (or probably any Windows Mobile phone), you need to put the file in the Storage\Application Data\Sounds folder.
Once you’ve done this it shows up in the list when you’re choosing your ring tone. You can also put it in the \Windows folder, but this folder is flushed every time you reboot your phone, so it will work until you turn your phone off and back on, and then the file will be gone.