These free add-ins for Word, Excel, and PowerPoint enable those apps to open and save their ODF counterparts (which typically have .ODT, .ODS, and .ODP extensions, respectively).

I also tested the plugin with a highly complex ODS file. In Excel, users load ODS files by clicking a special button in a toolbar rather than using the regular Open operation from the File menu.

How to Open Excel 2007 Files As Separate Windows. If you work with multiple Excel files over the course of a workday, and especially if you use a dual-monitor setup, you might wonder how you can ...