I just installed a new Win8.1 computer containing Office 2013. Previously I was using Office 2003, so my Word docs were .doc and excel files .xls.
I opened a workbook from 2003. When saving it, using the Compatibility option I converted to 2013.
Now, when I save the workbook I get the following message (see screenshot). FWIW, this workbook has multiple worksheets.
I'm not sure why I'd get this msg since I'm going from an OLDER version to a NEWER version. I'd expect to see it when going the other way.
So I guess I need to know why I'm getting the msg, and how to identify where in the workbook the problem is located.