When trying to update SQL Server 2012 with the patch KB2716442 (Windows 8) I was not able to solve the issue 84B20001.
Going on http://support.microsoft.com/kb/2716442 I was not able to solve the issue neither so I wanted to share how I solved this issue.
To solve the issue type "Regedit" in your start menu.
UPDATE 01/26/2013 :
Some comments describe that depending on your SQL version you might want to change other keys. For example setting the registry key "HKLM\SOFTWARE\Microsoft\Microsoft SQL Server\110\ConfigurationState" to 1 helps completing some installations.
Thank you for sharing your experiences.
You might have some Keys with a value of 3. Change all the keys so that they have a value of 1.
This operation works for SQL Server 2008, SQL server 2008 R2 by using the node 100 in the regedit and SQL server 2012 uses 110.
Hope this will help you.