function changeSupportProduct() {

  var product = document.supportform.product[document.supportform.product.selectedIndex].text;

  if(product == "Adcon") {
    document.supportform.mbrd_manu.className = "";
    document.supportform.mbrd_type.className = "";
    document.supportform.cpu_type.className = "";
    document.supportform.cpu_clock.className = "";
    document.supportform.os.className = "";
    document.supportform.driver_version.className = "";
    document.supportform.usbhost.className = "";
  }
  else if(product == "Ucon CX") {
    document.supportform.usbhost.className = "requiredfield";
    document.supportform.mbrd_manu.className = "requiredfield";
    document.supportform.mbrd_type.className = "requiredfield";
    document.supportform.cpu_type.className = "requiredfield";
    document.supportform.cpu_clock.className = "requiredfield";
    document.supportform.os.className = "requiredfield";
    document.supportform.driver_version.className = "requiredfield";
  }
  else {
    document.supportform.usbhost.className = "";
    document.supportform.mbrd_manu.className = "requiredfield";
    document.supportform.mbrd_type.className = "requiredfield";
    document.supportform.cpu_type.className = "requiredfield";
    document.supportform.cpu_clock.className = "requiredfield";
    document.supportform.os.className = "requiredfield";
    document.supportform.driver_version.className = "requiredfield";
  }
}

function changeSupportOS() {

  var os = document.supportform.os[document.supportform.os.selectedIndex].text;
  if(os == "Windows NT4" || os == "Windows 2000" || os == "Windows XP Home" || os == "Windows XP Pro") {
    document.supportform.os_sp.className = "requiredfield";
  }
  else {
    document.supportform.os_sp.className = "";
  }


}