DavidR
2
avast doesn’t automatically delete file it requires user input or to have been set-up to do so. The usual default action recommended by avast is Move to the Chest. Deletion isn’t really a good first option (you have none left), ‘first do no harm’ don’t delete, send virus to the chest and investigate.
Have (or did) you have another AV installed in this system, if so what was it and how did you get rid of it ?
Can you log in to safe mode, keep tapping F8 on boot, you should get an option to boot into safe mode ?