If you intentionally or accidentally modify ACLs on key system directories like C:\ or C:\Windows or C:\Windows\System32, your Windows 7 installation may behave unpredictably or even fail to work at all. Is there a way to re-apply default out-of-the-box NTFS security settings a hosed Windows 7 installation?
Unfortunately the only supported method is to reinstall Windows on the computer. Even in Windows XP, the approach of using Secedit to reapply the setup security.inf template was not a supported way of restoring the default ACLs on Windows XP either.
Mitch Tulloch is a seven-time recipient of the Microsoft Most Valuable Professional (MVP) award and widely recognized expert on Windows administration, deployment and virtualization. For more tips by Mitch you can follow him on Twitter or friend him on Facebook.