they where located in IE and Java temp folders so you can delete…
how ever there is usually no rush to delete from chest…thats why it is there, to keep the files for a while to see if something was wrongly detected (false positive)
if so you have the options to restore the file when the false detection is fixed
Clean, Quarantine, or Delete? http://antivirus.about.com/b/2007/03/11/clean-quarantine-or-delete.htm
how to use the chest http://www.avast.com/en-no/faq.php#tab4