Hre's a quick and dirty method:
Assuming the first 20 sheets in the book are the ones you want to copy and the sheet you want to copy to is named "ALL SHEETS":
Sub Copy_All_Sheets()
Sheets("ALL SHEETS").Select
Cells.Select
Selection.ClearContents
[a1].Select
where = [a1].Address
For i = 1 To 20
Worksheets(i).UsedRange.copy Destination:=Worksheets("All Sheets").Range(where)
where = [a65536].End(xlUp).Offset(1, 0).Address
Next
End Sub
I'm using Excel 2002