hi AZKID,
These errors reported are a result of avast! attempting to open these archives. It cannot do so as it does not know the password for that particular archive.
It does not mean the file is corrupted, only that avast! cannot open it to scan. One common mistake is to delete these archives because of this reported error; normal options are not available for the user. Leave these files alone; all avast! is reporting is that it cannot scan them.
Archived files cannot be run by themselves. They are static/inactive/compressed files until the user chooses to run them. A setup file for a program would be one such.
If you wish, you can exclude these files from scanning by avast!
Open avast! program (gui)>Settings>enter your password if needed>Global Exclusions. Enter the file path for each of your archived files. Click OK when done. What this will do is tell avast! not to scan these files when a manual scan is done. It also will exclude real-time scanners from monitoring them as well.
A quick scan once a week is usually sufficient for a clean system as avast! real-time shields should prevent any malicious files from entering your system; full scan is to be used only when quick throws a detected instance.
Hope this helps.