lately when i scan my computer (it scans every night
why every night..... you have a antivirus with realtime protection, meaning any file that moves when the computer is on is checked

files that can not be scanned (for whatever reason avast give) are just that, it does not mean they are infected
avast just give you a scan error report. files not found error is usually gone if you reboot and scan again

files that could not be scanned, is the most frequently asked question in the forum so lots of info if you search