Allow me to update you on the issue.

I was following the information given by Essexboy (http://forum.avast.com/index.php?topic=53253.0), as follows:

  1. I have installed Malwarebytes’ Anti-Malware.

  2. I ran it.

  3. It found no viruses in MBR, but found one in a completely different file, an executable downloaded from the internet.

  4. I have removed the infected executable file by Malwarebytes’ Anti-Malware.

  5. And that was it, the virus in MBR is now also gone. I checked it several times with avast! Internet Security and Malwarebytes’ Anti-Malware.

I don’t understand what really happened, but I guess that the infected executable file was contaminating my MBR. The trouble is, avast couldn’t find this file, and was repairing MBR only. I could be wrong.

Anyhow, my system seems to be clean now.

Thanks again to Pondus and Essexboy :slight_smile: