If I were to uninstall Avast! 4 Home Edition, would all my infected files and system files be deleted during the uninstallation process? 
thx
No, infected files on computer won’t be removed.
avast uninstallation removes only its own files.
If you’re asking about the files into avast Chest (Quarantine), oh, yes, they were removed on uninstallation.
If you want to keep them, extract them before to a folder of your choice and uninstall avast.
By the way, why are you uninstalling?
Welcome to avast forums.
Yes if you are talking about the files in the avast chest.
The files in the System Files section are back-up copies of your original system files and it isn’t a problem if they are deleted on uninstall as they aren’t in use.