Sorry Tech but the problem persists.
I have solved it in another way.
First of all when I wrote in run menu gpedit.msc it gives me an error that says "Unable to initialize..etc.."
So I have found on another ITALIAN Forum that I must re-register the dll files which need to gpedit.msc function.
I write on run menu:
regsvr32 gpedit.dll [Enter]
regsvr32 fde.dll [Enter]
regsvr32 gptext.dll [Enter]
regsvr32 appmgr.dll [Enter]
regsvr32 fdeploy.dll [Enter]
Then I retry gpedit.msc [Enter] and it runs!!
So I restart Windows and AVAST is recognized!
I've found a problem registering appmgr.dll and gpedit.dll files.
It gave me "unable to find the module"
So I check environmental variables and I noticed that there were
Path=C:\Windows\System32\Wbem
In this folder there's framedyn.dll file which need to register gpedit.dll!
In my hard disk the folder Wbem is written with first letter small,so I corrected in:
Path=C:\Windows\System32\wbem
When I tried to register appmgr.dll and gpedit.dll it didn't give me the error.
Sorry for the translation,if somebody had the same problem please write this down in a better form so they'll understand.
Thanks