Open the registry editor and browse to the following key:
HKEY_LOCAL_MACHINE \\ SOFTWARE \\ MICROSOFT \\ WINDOWS \\ CURRENTVERSION \\
POLICIES \\ RATINGS
Click on the Key (folder) named Ratings in the left pane of Regedit. In the
right pane, you will see a binary value named key that has a hexadecimal
string that represents the content advisor password in encrypted form.
Right-click on this value and choose Delete. Exit the registry editor.
Now you need to open Windows Explorer and delete the file
C:\\WINDOWS\\SYSTEM\\RATINGS.POL.
Once the registry value and the file have been removed, reboot your
computer. Now, if you open Internet Explorer and go to Tools/Internet
Options and click the Content Advisor tab, you'll see that the Settings
button is now grayed out and the Enable button is visible. It is as if
content advisor were never enabled.