Problem to open up .xls file on Office 2010

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What steps will reproduce the problem?
1. Use your ExcelLibrary.WinForm application
2. Create test xls with it.
3. Try to open it up in Excel 2010

What is the expected output? What do you see instead?
Excel found unreadable contant in newdoc.xls. Do you want to recover the
contents of this workbook? If you trust the source of this workbook, Click yes.

What version of the product are you using? On what operating system?
Windows 7 Enterprise x64 / Office 2010 Professional Plus, newest version from
here.

Please provide any additional information below.

```

Original issue reported on code.google.com by `evotect...@gmail.com` on 4 Jul 2010 at 2:55

Start by reproducing the reported steps with the ExcelLibrary.WinForm application: create a test .xls file and open it in Excel 2010 on Windows 7. Compare the generated workbook with the unreadable-content warning; done means Excel 2010 opens the generated file without asking to recover its contents.

Written by the indexing model from the issue text.