I suggest:

  1. Schedule an avast! Boot time scanning…
  2. If you can’t, or do not want, boot on DOS and run F-Prot or BitDefender for DOS from a CD
    You can try avast! Virus Cleaner Tool
  3. Clean your system (make sure of this)
  4. Please, tell us what files are into the Chest (could avast! make a list of them?)
  5. Try to restore the files to their original place (they will remain in Chest until you delete them).
  6. Delete the files from Chest.
  7. Uninstall avast! if you want…

Hope this help (like Pavel says everytime ;D)