Full scan can take a while. All depends on the size of your HDD and the amount of data you have in it. Also how you set up the sttings for full scan. Boot scan usually will analizy all files and HDD you have in your computer and it is slower.
First do no harm. Deleting the files is not recommended as first choice. Send the files to Avast! virus chest.
Clean, Quarantine, or Delete? http://antivirus.about.com/b/2007/03/11/clean-quarantine-or-delete.htm