For starters:-
http://androidforums.com/android-lounge/5349-help-us-help-you-your-problem.html
I don't know what phone your using, this information wil help alot
Secondly, now this is merely an assumption. I have the HTC Hero, now to add your own ringtones/message tones you only need to do a few things.
- create a folder in your SD card/internal memory called 'audio'
- in the audio folder add a 'ringtones' folder, a 'notifications' folder and an 'alarms' folder
- put mp3s for ringtones in the 'ringtones' folder, mp3s for notifications in the 'notifications' folder and mp3s for alarms in the 'alarms' folder
- restart your phone
- your tones should appear in the phone default menu's of ringtones, notifications and alarms
- any time you add new tones remember to restart the phone
Remember to keep the case on the folders as printed here. This is a long shot but my belief is that this ringtone trick runs across the android platform. Please try it and post PM your results regardless of sucess or not.