If you’re running two antivirus (and specially Norton) at the same time, quickly UNINSTALL one of them… you could lose the possibility of even booting the computer sooner or later… :o
avast is not compatible with Norton.
If you want to uninstall Norton, follow this:

  1. Remove NAV through Add/Remove programs from Control Panel. Boot.
  2. Use Symantec removal tool following the three steps defined in the SymNRT tool info.
  3. Boot.
  4. Install avast! Boot.

Well, if it was in Chest now, you can know what you’ve deleted, which virus was on it…
Chest is safer than just delete.