You subject line says Excel 97 but you post suggestes 2007.
Pivot tables made in 2007 are not compatible with 2003. When a 2003 user
opens them they will not be able to do anything with them. When they are
returned to 2007 the will regain their functionality.
If you want to make a pivot table compatible - open Excel 2007, save the
file as a 2003 file, close the file and reopen it in compatibliity mode.
Make your pivot table. Save and close it. Open it in 2003. It will work.