@DavidR yeah I forgot that lol ... chest files are encrypted anyway (quarantine process) and won't be accessible from an external system. Thing is the guy can't boot the infected system anymore. Remains index.xml, well there's no reason for this one to be encrypted and that would give an idea of what happened.
The index.xml is not encrypted and will provide the basic info original file name, location and Virus, etc.
So yes it will give an idea what happened - But I'm still wondering what it is that the OP is hoping for in trying to send the files to avast. Whilst they may possibly be able to decrypt them, if there isn't a unique encryption key created for the users system and not a common encryption key for the chest
