See the HELP section for a good explanation of the ####.  It could be that
your column is just not wide enough to display the entry.

If you are trying to add LEADING zeros to a string, type an apostrophe
first.  It will not show up on the cell, only in the formula bar, and changes
the cell format to TEXT.  Or, you can just format the cell for TEXT before
inserting the leading zeros.

Vaya con Dios,
Chuck, CABGx3

A cell with ##### generally indicates the column is not wide enough to
display the value stored: make the column wider by pulling the bar between
the column headers (to make column B wider, pull the bar between B and C) 0r
use Format Column and change the width. A negative date value can also cause
cell to show ###

If you want to see 0123 and not 123: type a single quote (') then the digits
OR format the cell with Custom Format 0000.

best wishes

one guess on your 2nd question

Type a preceding apostrophe if you want leading zeros
eg: enter it as '090
The apostrophe won't display in the cell, but it'll become a text number

One more suggestion for the ####  could be negative date or time.

And another.

If you have between 255 and 1024 characters in the cell and are formatted to
Text, you will get the #####.

If that is the case, format to General.

Gord Dibben  MS Excel MVP