Can someone help me figure out why this macro works in Excel 2003 and not in Excel 2000

I developed these worksheets on my computer which has Excel 2003. They need to run on another computer that uses Excel 2000.

I'll appreciate any help I can get on this. The sooner, the better

Private Sub Workbook_Open(
' Documented: http://www.mvps.org/dmcritchie/excel/insrtrow.ht
' Insert Rows -- 1997/09/24 Mark Hill
'Dim vRows As Intege
' row selection based on active cell -- rev. 2000-09-02 David McRitchi
Cells(65536, ActiveCell.Column).End(xlUp).EntireRow.Selec
' ActiveCell.EntireRow.Select 'So you do not have to preselect entire r
vRows =

' If vRows < 1 The
' vRows = Application.InputBox(prompt:=
' "How many rows do you want to add?", Title:="Add Rows",
' Default:=1, Type:=1) 'type 1 is numbe
' If vRows = False Then Exit Su
' End I

'if you just want to add cells and not entire row
'then delete ".EntireRow" in the following lin

'rev. 2001-01-17 Gary L. Brown, programming, Grouped sheet
Dim sht As Worksheet, shts() As String, i As Intege
ReDim shts(1 To Worksheets.Application.ActiveWorkbook.
Windows(1).SelectedSheets.Count
i =
For Each sht In
Application.ActiveWorkbook.Windows(1).SelectedShee t
Sheets(sht.Name).Selec
i = i +
shts(i) = sht.Nam

Selection.Resize(rowsize:=2).Rows(2).EntireRow.
Resize(rowsize:=vRows).Insert Shift:=xlDow

Selection.AutoFill Selection.Resize(
rowsize:=vRows + 1), xlFillDefaul

On Error Resume Next 'to handle no constants in range -- John McKee 2000/02/0
' to remove the non-formulas -- 1998/03/11 Bill Manvill
Selection.Offset(1).Resize(vRows).EntireRow.
SpecialCells(xlConstants).ClearContent
Next sh
Worksheets(shts).Selec

End Su

Thank

Leslie Barberi