The file XXX.xls may contain features that are not compatible with XML Spreadsheet 2003

Problem

You get this error when exporting data using the Export to Excel feature:

The file XXX.xls may contain features that are not compatible with XML Spreadsheet 2003. Do you want to keep the workbook in this format?

To keep this format, which leaves out any incompatible features, click Yes.

To preserve the features, click No. Then save a copy in the latest Excel format.

To see what might be lost, click Help.

You see this message while trying to save the exported Microsoft Excel to your disk. This message indicates that the XML spreadsheet format cannot save various types of objects and data.

When you save a Microsoft Excel workbook in XML Spreadsheet format, the following types of objects and data are not saved with the file:

OLE objects (such as embedded documents or objects from another program)
Pictures
Drawings and AutoShapes
Charts
Microsoft Visual Basic for Applications (VBA) projects
Group and outline information
Custom e-mail envelope information
Custom named styles that are not being used by any cell in the workbook

Solution

Click ‘Yes’ to keep this format which leaves out any incompatible features. Click ‘No’ to preserve the features. Then save a copy in the latest Microsoft Excel format.

http://support.microsoft.com/kb/287739