Hi,
You can do this many ways, some already mentioned:
1. Format the cell to Text, then type the numbers in with leading 0's
2. Start the entry with an apostrophy '0001234
3. Format the cell to Custom 00000 adding as many zeros as you want to show.
4. =RIGHT("00000"&A1,5) this will create a cell which packs leading 0's up
to five characters in all.
With numbers 1, 2, 4 above the cell actually contains the digits, with #3 it
is strictly a format, the cell does not contain the leading 0's.