raduius75 Could you be more specific about the location of that chest/index.xml?
I had a quick look through AVAST's many folders and files I couldn't find anything like that.........................OK just found it.
The Avast "chest" folder containing the index.xml is actually one of those normally hidden system folders found in ProgramData > AVAST Software > Avast > chest. To view it most Windows users will have to change their file/folder View settings to display the, typically, C:\ ProgramData folder location.
Such system folders are hidden for good reason so be careful. I'd recommend returning the View settings to hide them again once done.