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 Computername\Username) 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.

i have the same problem...please help!!!

I think it will work if you create an other account which is member of the Administrators group and via that account reconfigure the permissions of the registry key again. If that doesn't work, try to fix the permissions using the psexec tool using the following commandline. This will run the Registry Editor as the System account (check the Task Manager).Good luck!

great solution arris!!! thank you very much!!!

unfortunately after i restore permissions in product options back to the way they were avast! will not update!!!

i get the error message : Your operating system does not meet the requirements. This edition of avast! cannot be installed on Windows Server.

i guess it checks for the operating system version before updating every time!!!!

i think i will have to stick with system center 2012 endpoint protection!!!