how to set proxy setting for mozilla for win xp and 8

Question

To set proxy i access pref.js file and write following piece of code:

 first access path :

 Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData) + @"\Mozilla\Firefox\Profiles\"

 

And then set proxy to 5 for win 7 :

 

string str = File.ReadAllText(arrProfDirs[i] + "\\Prefs.js");
if (str.IndexOf("user_pref(\"network.proxy.type\", 5);") == -1)
{
str += "user_pref(\"network.proxy.type\", 5);";

}

 

in this way i did for win 7. what should i make changes to this code to set proxy for win8  and xp?