If you install Windows 8 Release Preview using the Windows 8 Release Preview Setup program, you won't need to enter a product key—the setup program automatically provides the product key. If you create installation media, start your PC from the media, and then install Windows 8 Release Preview, you'll need to enter this product key: TK8TP-9JN6P-7X7WW-RFFTV-B7QPF.
Windows Media Center is not preinstalled in Windows 8 Release Preview. If you want to use Windows Media Center, you need to add it by following these steps:
Swipe in from the right edge of the screen, and then tap Search.
(If you're using a mouse, point to the upper-right corner of the screen, and then click Search.)
Enter add features in the search box, and then tap or click Add features to Windows 8 .
Tap or click I already have a product key.
Enter this product key: MBFBV-W3DP2-2MVKN-PJCQD-KKTF7 and then click Next.
Select the checkbox to accept the license terms and then click Add features.
Your PC will restart and Windows Media Center will now be on your PC and the tile will be pinned to the Start screen.