Problem with WAVEHDR value during playback...waveapi misbehaving...

I am writing a USB audio driver for playback for wince 6.0. I play a
wav file (16 bit 48khz stereo) using Media player (that uses my driver
for playback). When i select a wav file for play then WODM_Write is
called..Here i got to know that WAVEHDR is receiving inapproriate
value i.e. pWaveHdr->lpData (Long pointer to the address of the
waveform buffer) is having value 0x00. As per my understanding this
behaviour is improper, it should be containing the data for playback
that is retrieved from wav file..Can you please tell me how can i get
proper WAVEHDR value.
please let me have feedback.
Thank you for your anticipation in advance.

FYI:
The WindowsCE.Net DDK says if MMSYSERR_NOTSUPPORTED is returned for
WODM_PREPARE & WODM_UNPREPARE IOCTLs then the waveform API manager
will handle these IOCTLS. My driver does return MMSYSERR_NOTSUPPORTED
for these IOCTLs.

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