Thanks a lot David. Now I get the clear picture.
Just one query.... in the System Files section, I have four system files. So does it mean that the originals of these system files have become infected? In that case, after i do a thorough scanning, the scan report or the SUI should tell me that four files are infected. But it is not doing so.
Or did you mean to say that in the System Files section, Avast keeps back-up copies of important system files in case the original becomes infected in future...?
Another thing i notice is that in my System Files section, there's one system file that doesn't bear the "---no virus---" sign, while the rest of the system files do.
Dev
India