I've been trying to figure this out and have succeeded (Huzzah), so
I'll share it with all. I have a Smartphone with WM5. I the really
annoying and dare I say, uncreative alarm clock sounds provide with the
OS. So since I can play mp3s with my Mobile Windows Media, I thought,
why not make an alarm based off of it?
This is how you do it: Take your mp3, and decompress it to a WAV file.
You will probably have a big WAV file (my phone doesn't pack a lot of
internal memory ~ 32MB I think). So, you can use the WAV compression
level that the other sounds have: 11025 Hz, 16-bit, Mono. So once you
recode (or down-code, haha) then make sure to copy it into the \Windows
directory on your mobile device. Now, when you configure your alarm
(not reminders for events, but straight up alarm clock) you can tell it
that new song you just added. Voila! Have fun waking up to your
favorite song!