If you plan to share your Excel 2007 files with others, set Excel 2007 to save your files automatically in Excel 97-2003 format, so anyone can open them.
How to do it:
1. Start up Excel 2007. Open an empty work sheet.
2. Click the “Office” button at the top left to bring up a menu.
3. Click the “Excel Options” button at the bottom of the window. You’ll see a list of options to the left, headed “Popular.”
4. Click on the fourth one down, “Save.” Next to “Save files in this format,” you’ll see a box that says “Excel Workbook (*.xlsx).”
5. Click on the down arrow at the right of the box and a list appears.
6. Click on “Excel 97-2003 Workbook (*.xls).”
7. Click “OK.”
To check to see that your change has worked: Click on the colored “Office” button again. This time select “Save As.” At the bottom of that box, it should say “Save as type Excel 97- 2003 Workbook.” Other Excel users can now view your data.