I installed avast in administrator account in this guide:
1.) Start –> Run –> Regedit
2.) Go to HKEY_LOCAL_MACHINE –> SYSTEM –> CurrentControlset –> Control
3.) Now change the permissions of the folder “ProductOptions” –> add your user account (for example ComputernameUsername) and deny yourself the read rights for the whole folder.
Now how to restore permissions in “ProductOptions”? I can not read this registry key with the administrator account.