with true numbers, leading zeros are unnecessary so xl drops them. preformat
the cell as text or being input with a leading apostrophe.
you can create a custom format such as "00000" but this would only make the
number to "appear" to have a leading zero. in the fomula bar, there would be
no leading zero. this creates problems when you try to export becasue the
leading zero is not really there. it may create problem when you copy/paste
but that depends.