Note that the files are into System folder, they are back-up copies of important system files. There are (generally) files in the System Folder of the Chest: command.com, kernel 32.dll and wsock32.dll. During the installation, avast! copies some critical system files into the Chest, under the "System files" category. Those files might cause the operating system to crash if they get infected by a virus. If needed, those files can be restored from the Chest to their original location. Should an unknown virus infect the computer despite the extensive protection from the avast! antivirus package and alter an important system file, it can then be easily restored to its original state.