Cannot directly open Excel files

[DDE12]

I recently installed some of the Excel built-in add-ins on both of my PC's and now I cannot directly open Excel files when double clicking on them. Double clicking an Excel file results in Excel opening but with no spreadsheet at all. Just the blue background. I can open spreadsheets by going to Open or by clicking on one of the recent files. I disabled all of the add-ins but did not resolve the problem. I would greatly appreciate some help in troubleshooting. Thanks in advance.

[5631]

Excel 2003
Extras = Options = General and deactivate
"Ignore other Applications".

Excel 2007
https://www.think-cell.com/en/support/kb/0045.shtml

[DDE12]

Sorry, I should have indicated I had Excel 2007. I tried the link, but unfortunately that did not work. My problem is a little different in that Excel will open but the spreadsheet I'm trying to open will not.