Did you install it as Administrator?
It could be some of the Microsoft Services affecting the installation.
Did you follow the permissions route as per this?
Saw this comment in another forum:- "My husband was able to get it installed. At the beginning of the install there is a box checked that says something to the effect it will try to authenticate the license while doing the install. He unchecked that and the install completed! Once complete, he opened a work doc and was prompted for the license key and it took it at that point and we're good to go."
Alternatively you could do it from a clean boot, which many users have had to do - see this link