Hi Craig Beuker,
Thank you for using Syncfusion product.
We currently do not provide the support for creating the pivot table for Excel 2003 format. We highly regret for the inconvenience.
For more information,please go through our following online link.
http://help.syncfusion.com/Ug_101/Reporting/XlsIO/ASP.NET/default.htm#!Documents/pivottables.htmThanks for your detailed update. Please let us know if you need any clarifications.
Thanks,
Manikandan.M