Windows 7

Delete C:\Windows\CSC\v2.0.6\namespace, CscService

Open comand prompt in “Run as administrator” mode:

Stop sync service:

net stop CscService

Disable sync service:

sc config CscService start= disabled

Take ownership of c:\windows\scs:

takeown /f c:\windows\csc /r /a /d y > NUL

Reset permissions:

icacls c:\windows\csc /grant Administrators:(F) /t /l /q

Remove directory:

rd c:\windows\csc /q /s

Enable sync service:

sc config CscService start= auto

If something fails you can move to safe mode and repeat the steps.
Make sure you have at least one local administrator account active.
Just hold down the shift key and choose to restart the computer.