Before you enter your number, format cell as Text

or:
type an hyphen ' before your number

HTH
--
AP

H

Prefix with a single apostrophe (') (it won't show or pre-format the cell as
text or...

If all these are the same length format (Format>Cells...Custom) as

0000000000

Depends on exactly what you want to do with the number.

To use as text with no calculations (credit card numbers - model numbers),
on a cell by cell basis, you could prefix the entry with an apostrophe (
'01234 ), which is *not* visible in the cell, but can be seen in the formula
bar,
OR, for large ranges,
*Pre*format the column (range) as 'Text'.

To use the numbers in calculations,
Custom format:
0000000000
Which will display leading 0's for less then 10 digit numbers.

if the number always starts with a 0 then you can format your cell

right click on the cell and select format cells,numbers,custom
in the type box enter this
0#########
then enter
now when ever a number is entered into that cell a zero will appear
first

Thanks for the replies :)