|Check the Properties of the file and see what it says.|
Go to the directory where the file is located.
Possibly "My Documents"
Select the file, but do not open it, just highlight it.
Right click on the file.
A window/menu should open.
At the bottom click on Properties
Another window/menu should open.
Near the top will be two lines:
Type of File:
Should say something like, Microsoft Office Excel Document.
Should say Microsoft Excel
If the Open With: does NOT say MS Excel
click the Change button next to it and select MS Excel from the window/menu that should appear.