Mine

/*
    String getOS()
    Returns the current running Operating system name
    by -dt-
*/
function getOS(){
	var details = new ActiveXObject("WbemScripting.SWbemLocator");
	var serv = details.ConnectServer();
	
	var x = serv.ExecQuery('SELECT * FROM Win32_OperatingSystem');
	for(var enume = new Enumerator(x);!enume.atEnd();enume.moveNext()){
		return enume.item().Caption;
	}
    return "";
}

Debug.Trace(getOS());