I was infected a few months ago and got rid of all the viruses thanks to your program. I have not had any problems since and no viruses found lately but i was just messing around and looked in the chest folder and found this file was never deleted. frmwrk32.exe.vir It was located in my system32 and i always though you weren't suppose to delete files from your system32, Although if this is part of a virus i'm sure it needs to go. Just though i would ask if it will do any harm to my PC if i delete it, if it is a needed file to run properly or if it is just a file a virus put in there.
First I suspect this isn't in the chest but in the Moved folder (see image) and the reason it is there and why it has a .vir suffix is that when avast detected it you elected the move rename option. When you do that avast moves to the file to the Moved folder and appends the .vir suffix to the original file name.
Second, avast doesn't delete or move or otherwise, that is down to you, the user who makes the decision on what action to take. avast merely scans and alerts to infection and gives you option on actions that you can choose, delete (not good), move/rename, move to chest (best option), etc.
Files in the system folders that are genuine system files, etc. can get infected, but more importantly malware can easily place its files in the system folders. They can do this because if you use an account with administrative privileges, any malware inherits those same privileges; this allows them free reign to do almost anything, place files in system folders, create registry entries, etc.
You can run using a limited user account and this also limits the potential for damage it can cause.