Please quote the FULL EXACT error message you get when opening Excel.

The actual Icon makes no difference to what program opens a fule - it's
merely an indicator.
That said, you would appear to have change the association for XLS files.
First, do a search for the Excel executable (or look at the properties for
the Excel shortcut) make a note of the path to the Excel.exe file
Go to Folder Properties, and click on the File Types tab,
look in the list for the XLS entry, highlight it, and click 'Edit'
In the list of Actions, highlight the 'Open' entry
click Edit
now copy the full path to the excel executable into the 'Application used to
perform action' box (or use browse to point to the file), making sure that
the path is enclosed in double-quotes
.
At the end, append a /e switch.
the full entry should therefore look something like this.....
"C:\Program Files\Microsoft Office\OFFICE11\EXCEL.EXE" /e
when complete, OK out
and try the file again