Without some information on the file names and locations (screenshot of the scan log) or copy and paste from the scan log text file (see below), no one can say why A) these might have been detected and crucially B) why they couldn't be dealt with (move to chest, etc.).
Deletion is not a good first option (you have none left), 'first do no harm' don't delete, send virus to the chest (a protected area) and investigate.
Most of the log files are stored in the C:\Documents and Settings\All Users\Application Data\AVAST Software\Avast\report (XP location) or C:\ProgramData\AVAST Software\Avast\report (Vista, win7 location). It depends on what the scan you did was called as to what file to look in for the information.
Edit: duplication of location.