We have an application that exports data using the older Office XP/2003 XML Spreadsheet format. These files are saved with a .xls extension so that they can be launched directly, without having to know the installation of Excel.
This has worked extremely well for us up until now. However, we have just recently upgraded to Office 2007, and when we launch these .xls files directly, Excel 2007 shows a warning message:
The file you are trying to open, 'file.xls', is in a different format than specified by the file extension. Verify that the file is not corrupted and is from a trusted source before opening the file. Do you want to open the file now?
I have already tried adding the location of the file to the "Trusted Locations" in Excel, but the warning message still comes.
Is there any way to suppress this message?