You could use a very simple bit of code:-
Sub UnhideAllSheets()
For Each s In ActiveWorkbook.Sheets
s.Visible = xlSheetVisible
Next
End Sub
HTH,
Dan.
...there may be a more scientific way but I simply record a macro the first time that I unhide them (tools-macro-record new macro)and then use this subsequent times - connected to a button on a worksheet this is a one-click operation to unhide all required sheets......if it is for client use you can record the macro in a different workbook so that only you have access to it...