Obtain your key here
http://technet.microsoft.com/en-us/windows/dd353205.aspx
This is what you will see :
Windows 7 Beta 64-bit Product Key
You may use the following product key to activate your evaluation copy of Windows 7 Beta 64-bit.
Product key: XXXXX-XXXXX-XXXXX-XXXXX-XXXXX
Please print this page for your records.
We're sorry, but downloads are no longer available. Here are the Installation Instructions, Release Notes, and FAQ.
NOTICE ABOUT THE H.264/AVC VISUAL STANDARD. This software includes H.264/MPEG-4 AVC visual compression technology. MPEG LA, L.L.C. requires this notice:
THIS PRODUCT IS LICENSED UNDER THE AVC PATENT PORTFOLIO LICENSE FOR THE PERSONAL AND NON-COMMERCIAL USE OF A CONSUMER TO (i) ENCODE VIDEO IN COMPLIANCE WITH AVC STANDARD (“AVC VIDEO”) AND/OR (ii) DECODE AVC VIDEO THAT WAS ENCODED BY A CONSUMER ENGAGED IN A PERSONAL AND NON-COMMERICAL ACTIVITY AND/OR WAS OBTAINED FROM A VIDEO PROVIDER LICENSED TO PROVIDE AVC VIDEO. NO LICENSE IS GRANTED OR SHALL BE IMPLIED FOR ANY OTHER USE. ADDITIONAL INFORMATION MAY BE OBTAINED FROM MPEG LA, L.L.C SEE HTTP://WWW.MPEGLA.COM