Just guesses...

The last used cell on each worksheet is way past where you think it should be.
See Debra Dalgleish's site to reset this last used cell.

http://www.contextures.com/xlfaqApp.html#Unused

Any chance you have objects (pictures/buttons/textboxes) in your workbook?

Sometimes pictures get duplicated by error.


Kerry wrote:

My company has been using an excel file from year to year for bank records.
Only 2004 and 2005 is included however, the size is enormous - 57 megs. What
could cause the size to be so large? Is ther any type of purge function?

--

Dave Peterson