Problem with FIREFOX portable

Hello,

In order to do a test, i have to use a FIREFOX PORTABLE, but there is the following message :

According to the specified parameters, the required browser is: Mozilla Firefox (x86) This browser was not found on the current computer, or it is not supported

function ListBrowsers()
{
  var browser;
  for (var i=0; i < Browsers.Count; i++) 
  {
    browser = Browsers.Item(i); 
    Log.Message("Browser " + aqConvert.IntToStr(i) + " : " + browser.Description);
  }
}