The leaked Windows 8 Build 7850 M1 Divulged contains a number of features which are currently no available for final use. This includes a new Windows Explorer with Ribbon UI, a dedicated Webcam app, a built-in PDF reader, Advanced Task Manager, and more.
Until the final version is released, you can do few changes in the Windows Registry to enable all these features. Also there is an app, Windows 8 Tweaker Tool available for download which lets you enable these features with one single click.
Windows 8 Tweaker Tool is available at both unofficial Windows 8 Search and Windows Beta sites and can be downloaded from here.