请各位高手，帮我看一下这个代码错在那里啊？我找了很久也找不到啊。谢谢！

<html>
<head>
<object classid="clsid:CFCDAA03-8BE4-11CF-B84B-0020AFBBCCFA" id="real1" width="20" height="20">
  <param name="height" value="0" />
  <param name="width" value="0" />
  <embed name="real1"
  id="real1"
  border="0"
  controls="play"
  height=0
  width=0
  type="audio/x-pn-realaudio-plugin">
</object>
<script language=javascript type=text/javascript>
var fileName="";
function butplay_onclick()
{
  document.real1.SetSource("file:///"+fileName)
  document.real1.Doplay();
}
function butStop_onclick()
{
  document.real1.DoStop();
}
function file1_onblur()
{
  fileName=document.form1.file1.value;
 }
 function  window_onload()
 {
    var plugInInstalled=false;
if(navigator.appName.indexOf("Microsoft")==-1)
{
  var plugInCounter;
  for(plugInCounter=0;plugInCounter<navigator.plugins.length;plugInCounter++)
  {
    if(navigator.plugins[plugInCounter].name.indexOf("RealPlayer")>=0)
{
   plugInInstalled=true;
   break;
   }
 }
}
else
{
   if(real1.readyState==4)
   {
     plugInInstalled==true;
 }
}
if(plugInInstalled==false)
{
  window.location.replace("NoRealPlayerPage.htm");
 }
}
</script>
</head>
<body onload="return window_onload()">
<noembed>
  <h2>this page requires a browser supporting plug-ins or ActiveX controls</h2>
  </noembed>
  <form id=form1 name=form1>
    <input type="button" value="Play Sound" id="butplay" name="butplay" onclick="return butplay_onclick()" />
<input type="button" value="Stop Sound" id="butStop" name="butStop" onclick="return butStop_onclick()">
<input type="file" id="file1" name="file1" onblur="return file1_onblur()">
</form>
</body>
</html>