How to Set Custom Message Tones
If want to change the messages tones with custom one, you can just do it on this simple way. Use your a file browser like ASTRO, which you can find on the market place under productivity.
Go to the Media folder, then Audio, then Notifications. You need to copy the mp3 into this folder.
Than you can select the tone you want on the ringtone list.
This can also be done by plugging in the USB and opening the storage device under windows. The mp3 should then be available to use when you select your notification tone, Hope this helps.
Source: http://androidforums.com
