I cannot get the initial value by "value"  when I use the  input type="file" in FORM tag. Here is my code,you can find my problem.

<html><title>example</title>
<script language="javascript">
<!--//
function init()

 document.form1.file1.value="C:\\MyeOffice\\popupmenu.txt"; 
 document.form1.file2.value="C:\\MyeOffice\\popupmenu.txt";
 alert(document.form1.file1.value); 
 alert(document.form1.file2.value);
 //C:\MyeOffice\popupmenu.txt
 
}
//--> 
</script>
<body onload="Javascript:init()">
C:\MyeOffice\popupmenu.txt
<form name="form1" method="post" action="up.asp" enctype="multipart/form-data">
<input type="file" name="file1" value="C:\\MyeOffice\\popupmenu.txt">
<input type="input" name="file2" value="C:\\MyeOffice\\popupmenu.txt">
<input type=submit name="submit" value="submit">
</form>
</body>
</html>