function checkOS() {

  if(navigator.userAgent.indexOf('Linux') != -1){
     var OpSys = "Linux";
  }
  else{
     if((navigator.userAgent.indexOf('Win') != -1) &&
          (navigator.userAgent.indexOf('95') != -1)){
        var OpSys = "Win";
     }
     else{
        if((navigator.userAgent.indexOf('Win') != -1) &&
          (navigator.userAgent.indexOf('98') != -1)){
        var OpSys = "Win";
        }
        else{
           if(navigator.userAgent.indexOf('Win') != -1){
              var OpSys = "Win";
           }
           else{
              if(navigator.userAgent.indexOf('Mac') != -1){
                 var OpSys = "Macintosh";
              }
              else{
                 var OpSys = "Other";
              }
           }
        }
     }
  }
  return OpSys;
}

//var OpSys = checkOS();