Macros: 2007 and 1997-2003 incompatibility

I've just found that the macros I recorded in 2007 for a simple data sort, i.e. highlight some cells and data sort, do not run when the spreadsheet is opened in Excel 1997-2003 after the original had been saved in the old format.There was a warning about slight loss of quality due to formatting but nothing else. Is there a simple way around this or do I have to rerecord all the macros in the old version?

Macros code for the sort is typically this:-

Sub Macro2()
'
' Macro2 Macro
'

'
    Range("M13:N18").Select
    ActiveWorkbook.Worksheets("FM I-O (B)").Sort.SortFields.Clear
    ActiveWorkbook.Worksheets("FM I-O (B)").Sort.SortFields.Add Key:=Range( _
        "M13:M18"), SortOn:=xlSortOnValues, Order:=xlAscending, DataOption:= _
        xlSortNormal
    With ActiveWorkbook.Worksheets("FM I-O (B)").Sort
        .SetRange Range("M13:N18")
        .Header = xlGuess
        .MatchCase = False
        .Orientation = xlTopToBottom
        .SortMethod = xlPinYin
        .Apply
    End With
End Sub