1. Have Office 2007 or 2010 installed on your computer and
2. Then install Office 365 and
3. Then uninstall the old version of Office…
You will probably discover that when you double-click on an Excel workbook (.xlsx, etc.) from within Windows Explorer, that Excel opens, but the spreadsheet doesn’t. You have to open the workbook from within the Excel application.
Fortunately, there’s an easy fix.
Go to Programs and Features in the Control Panel. Select Microsoft Office 365 from the list of programs and click Change. Select the Quick Repair radio button and click the Repair button.