Bob Phillips wrote:
There are no versions between 2003 and 2007,

Excel 2007 uses a different file format, they are zipped files of various
components, and because of this, MS use a different file extension to
signify 2007 files. xlsx are the 2007 equivalent to xls, files, are there
are also xlsm (macro enabled files) and xlam, equivalent to xla files. As
Shane said, anyone can download the free compatibility pack so that 2003
users can open the new file formats. The compatibility packs work well, but
if the 2007 files contain any of the new features of 2007, they will be
stripped out when opened in 2003 as that version knows nothing about them.

It is also possible to save a file in Excel 2007 in 97-2003 format. Such
files will have 65536 rows, 256 columns as Excel 2003 has, and when saved
new functionality is lost, but they can be easily opened in Excel 2003 with
or without the compatibility packs.


And if you wish to save in the 97-2003 format by default, you can click
the Office button Excel options at the bottom of the drop down and
then select save and set the default format there.

gls858