Speed Up VBA Loop Code

Try:

 Dim H As Range, I As Range, dd As Range
Set I = Range("E:E")
For Each dd In I.Cells
    If dd.Value = "1" Then dd = "A"
    If dd.Value = "2" Then dd = "B"
    If dd.Value = "3" Then dd = "C"
    If dd.Value = "4" Then dd = "D"
    If dd.Value = "5" Then dd = "E"
Next dd

Or you could use

Dim H As Range, I As Range, dd As Range
Set I = Range("E:E")
For Each dd In I.Cells
   dd = Application.WorksheetFunction.Choose(dd.Value, "A", "B", "C", "D", "E")
Next

Regards, TMS