Dick,
For what it's worth, you can always get Excel to try and open a file by first having the Excel window up on the screen, and then "Open" from the file menu. Then at the top or bottom of the file dialog window (Mac is on top, I think Windows at the bottom), there is a menu which says "Enable". The default is Excel files, but you can also choose the "All Files" option.
Now that doesn't mean it will actually be able to open the file (it does depend on what's in the file), but at least it will try. If it is a real Excel formatted file, or a tab or spaceor whatever delimited text file, it should work. At least is does on my Mac and I think on a Windows machine.