Perhaps you're a student who only needs Microsoft Office for a limited time. Maybe you want to kick the tires on Microsoft's office suite for more than 30 days or just don't want to plunk down the money for it yet.
Here's a way to extend the free trial period for Microsoft Office so you can get the full features without paying for it (for at least 180 days).
To do this, you'll need to find the Microsoft Shared folder under C:\Program Files\Common Files, then open a command window and run the Microsoft-provided utility, OSPREARM.EXE. Easy peasy.
The downside is you have to do this every 30 days (maybe set a calendar reminder?), but it's worth it if you want to get as much use out of your trial period as possible.
Don't forget, though, if your company participates in Microsoft's volume licensing program, you can get Office 2013 Professional Plus for just $10. That applies to many university students, major corporation employees, and even government employees (who aren't getting a lot of breaks lately).