title: Windows 7: "Excel found unreadable content"
body: <p>I'm using PHPExcel to generate a very simple .xls file (<code>PHPExcel_IOFactory::createWriter($PHPExcel, 'Excel5')</code>). Whenever that file is opened on Windows 7 using Excel 2010 or 2007, I get the following error: </p>
  
  <p><em>Excel found unreadable content in 'XXXXXXX.xls'. Do you want to recover the contents of this workbook? If you trust the source of this workbook, click Yes.</em></p>
  
  <p>When I open the same file in Excel 2010 in Windows XP it works fine. If I open the same file in OpenOffice, it works regardless of the OS.</p>
  
  <p>Windows 7 / Excel 2010: Error</p>
  
  <p>Windows 7 / Excel 2007: Error</p>
  
  <p>Windows XP / Excel 2010: Works</p>
  
  <p>Windows XP / Excel 2007: Works</p>
  
  <p>Any / OpenOffice: Works</p>
  
  <p>When I tell PHPExcel to generate an .xlsx file (<code>PHPExcel_IOFactory::createWriter($PHPExcel, 'Excel2007')</code>), it works fine with all the above combinaisons.</p>
  
  <p>I found countless threads on the MS forums, and it seems to affect only Windows 7 files with Excel files generated by third party libraries (not just PHPExcel). But no one has a solution.</p>
  
  <p>I also found the following MS KB article, but I'm not familiar with the underlying Excel specifications: <a href="http://support.microsoft.com/kb/2411912" rel="nofollow noreferrer">http://support.microsoft.com/kb/2411912</a></p>
  
  <p>Has anyone else experienced this?</p>