Delete that key, reboot then try SFC again.
If that doesn't work again:
Note:: Create a new system restore point before continuing.
Browse to the pending.xml file in winsxs, right click on it and then choose properties.
Click the security tab, then click the advanced button.
Click the change permissions button, then uncheck 'include inheritable permissions'.
Choose remove.
Click the add button, type everyone then click ok.
Check allow next to 'full control'.
Click ok on each of the windows.
Copy pending.xml to your Desktop, then delete the copy in winsxs.
Reboot your computer, then try to run SFC again.