I've right click on the icon in the systray, then chosen Start avast antivirus.
After memory test, click on the icon "Folder selection", and then check the box near C:. In selected paths, I have "C:\"
last thing I did click on OK.
After that, a screen telling me that scan local drives is set to off, scan removable media is set to off, scan selected folder is set to on. Then I click on the arrow ( start ).
I'm waiting for the result.