I would do the following:
Dictionary<string,string> ldict = new Dictionary<string,string>();
ldict.Add("English", "En.dll");
ldict.Add("German", "Ge.dll");
ldict.Add("French", "Fr.dll");
comboBox2.DataSource = ldict.ToList();
comboBox2.ValueMember = "Key";
comboBox2.DisplayMember = "Key";
Then in the select change you can get the value from the dictionary using the key that has been selected. There is probably a better way but I'm not sure what it would be.