After upgrading to Excel 2007, you may get the following error when you try to open an excel document:
The file you are trying to open .xlsx is in a different format than specified by the file extension. verify the file is not corrupted and is from trusted source before opening the file. Do you want to open the file now?
This errors particularly occurs when you’re trying to open an XLS file (Excel 2000-2003) with Excel 2007.
The easiest way to solve this problem, is to insert the following registry key. This will suppress the notification:
The step-by-step instructions are as follows:
- Click Start, click Run, type regedit.exe and press ENTER. This will open your Registry
- Navigate to HKEY_CURRENT_USER\SOFTWARE\MICROSOFT\OFFICE\12.0\EXCEL\SECURITY
- Right click in the right window and choose New -> DWORD
- In the Name field, type “ExtensionHardening” (without the quotes)
- Verify that the data has the value “0”
I advice the steps above to solve the problem, despite the fact that it is quick and dirty.
If you want a more constructive way, you should define MIME types and associate them with extensions.
When you use a Document Management System (like Sharepoint or Livelink), you can try adding these:
.xls = application/msexcel
.xlsx = application/vnd.openxmlformats-officedocument.spreadsheetml.sheet