.wav files can be created/saved in a number of ways using various bit rates and compressions, including .mp3. they still save as "*.wav" but are not necessarily the .wav format that dark basic expects so they'll give you the error. i expect windows media player (and other media players) know to look for extended information to sort out exactly what the .wav file is. alas, dbpro doesn't seem to do much (if any) of that. so...long story short, you'll need to take those .wav's and convert them to normal .wav files (or .mp3's, etc). i don't recall the specs dbpro (and windows/dx?) considers as standard .wav so you'll have to do a little trial and error. there's probably more than one and it shouldn't be too difficult a task (looking at the program i sometimes use for sound, i have my .wav files set to export as "Microsoft 16 bit PCM" and expect that will be successful for you).
oh, in case you need it, i use Audacity. it has some good features for sound (including many export options) and it's free/open source. you can find it here:
http://audacity.sourceforge.net/
good luck!
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