As always, Microsoft is offering its typical cheap upgrade period just before the launch of a new operating system. Microsoft usually offers a period during which a new PC can be bought and later upgraded to the latest version of Windows for cheap. They do this so as to not kill sales right before the launch.
The period started back in July and the end date has now been extended to around February 14, 2013. For a mere $14.99, you can update from Windows 7 to the latest and greatest, in some people's opinion, Windows 8 operating system. If you're planning on doing this, you can check out the full details from Microsoft's page describing the process.
KitGuru has reported the change, though the official Microsoft page is still saying January 31. Until Microsoft confirms the change on the above linked page, I would live by the January 31 date.