Properties dialog box opens instead of a workbook

[Guest]

When I open Excel (either by double-clicking the shortcut on the Desktop or
by opening an actual spreadsheet), I get the "Excel Properties" dialog box. I
can right-click and choose "Open With->Microsoft Excel" and it opens fine.
Everything was working yesterday and there were no changes to the machine or
any configuration files.

Any ideas why it would suddenly do that?

 

[Guest]

Correction:
The "Shortcut Properties" dialog box opens when opening the shortcut icon on
the Desktop. The file properties dialog box opens when trying to open an
Excel file.