"open with" not working in microsoft excel
 

I can open excel spreadsheet files just fine. But when I right-click on a
".txt" file and select "open with", Excel is not listed. So I select
"Choose Program". Again, Excel is not listed. So, I browse to EXCEL.EXE and
accept and nothing happens. It just goes back to the "Open With" screen and
Excel still is not listed. Any ideas?