Initialize primary buffer on open.

dlls/dsound/primary.c

@@ -132,6 +132,9 @@ static HRESULT DSOUND_PrimaryOpen(IDirectSoundImpl *This)
 
 		if (This->state == STATE_PLAYING) This->state = STATE_STARTING;
 		else if (This->state == STATE_STOPPING) This->state = STATE_STOPPED;
+		This->playpos = 0;
+		This->mixpos = 0;
+		FillMemory(This->buffer, This->buflen, (This->pwfx->wBitsPerSample == 8) ? 128 : 0);
 	}
 
 	return err;