Hmm, interesting. I'll just take some stabs at it. First make sure the filename in the ini is exactly the same as on the drive, capitalization and all. Second, try creating an MP3 from the wav and using that. Third, try using "startup_sound=/data/tts/Welcome.wav" to see if the file on the data partition plays. If those don't work, you could try using the "Welcome to PhatNoise.mp3" file that comes with the DMS just to make sure it's not a format issue, but I agree with you that your method should have generated a correct file.