Silent ringtone

Ok have a couple ringtones (.wav) I grabbed off the net. Fired up MPT and using Melody Maker previewed then transferred the files to the phone. During the transfer process the software changes the file format to .mp3. Exit the program, disconnect the phone. The added files showup in the sounds directory but when I try to use them as ringtones they are silent. Are there any common reasons for this that I've overlooked?
Thanks for any info.
On the good side I figured out how to remove an errant file name from my sound files list when I delete the file using something other than MPT.