One of the first things we noticed in the Windows 8.1 Preview was that the Libraries link was missing from the navigation pane. Here is how to get it back.
How to Get Your Libraries Showing Back in the Navigation Pane on Windows 8.1
Press the Win + E keyboard combination to open a new explorer window. Then right-click anywhere in the navigation pane and click on Show Libraries when the context menu appears.
That’s all there is to it.