I have worksheets created with Excel, perhaps as far back as Excel 4. They were last saved in Excel 2003, I believe in 2003 file format. When I try to save them using 2007 I get “[file name].xls cannot be saved in the current format. To save your changes, click OK, then save it as the latest format.”
I made no changes. I simply opened the file and hit save. This only happens to some files. I am trying to find a common denominator.