Sorry if the answer to my question has already been given.
First, about my notebook: ASUS X51RLseries; CPU Pentium DuoT2370 1,73 GHz; RAM 2 Gb; Windows Vista Home Basic SP2
Next is my problem. If I want to scan any folder, file or removable disk, I usually open Windows' context menu and choose to check that place. When I used Avast 4.8, it immediately showed its scan window and I could see all the process of scanning. Now, with Avast 5, the behaviour is a bit different: I right-click on the object of scanning and choose to scan it; at that moment my Windows Explorer becomes unresponsive for some time; then Avast's scan window opens behind the Explorer's one (the lattest became clickable) and when I move the scan window to the foreground, I see 80-90% of scan has already been done.
Why does context scanning hang up Windows Explorer? Why doesn't scan window appear before or at the very beginning of the scanning?