The Windows "Open With" dialog box will help you quickly reassign a default program for your Excel documents. Find an Excel document on your desktop. Excel documents may use the extension .xls ...

How to fix Excel file format and extension don’t match ... If the issue persists, the file could be corrupted, or your software settings may need checking. Try using an Excel repair tool ...

DAT files are files with an extension that isn't associated with ... you can convert the file into text in the Microsoft Excel program by first saving it as a CSV file. Right-click the DAT file ...

DDE stands for Dynamic Data Exchange; it is used to inform the particular software that a file with the extension you support is requested to open. If DDE is turned off in MS Excel then Excel will ...