WMP's problem

I am a programmer.Now I am doing a project using WMP to replay *.wav file
in webpage.I found that if the *.wav file I set to the URL parameter is a
local file or a file within local area network, when I replay it for the
first time,the position bar doesn't move correctly.At the beginning it moves
just a little,after that immediately returns to the startpoint leaving the
file playing till the end and can be not be stretched.But the second time of
replaying, it is all rigth,the position bar moves correctly.That only occurs
with *.wav file(*.mp3;*.wma;*.rm are all rigth) and when I replay a Internet
file(set the parameter URL to "http://*.wav") ,this problem doesn't exists.
Directly useing WMP applicatioon also has that probelm.It's esay to test.
Please open the WMP click file -url open,then fill in a local *.wav file
path(for excemple "c:\\abc.wav").please notice the positionbar.
All that occurs under ther version 7 above .
Thank you for reading this letter.I hope I can receive your reply.