The people who praises Norton Antivirus doesn't have enough background in the field, I believe.
My experience has proven that Kaspersky is the most stable/long term solution that consumes the lowers memory for the broadest set of features (while doing the job of course).
I use "McAfee VirusScan for Win32" to scan individual files, directories, or an entire drive. It's a simple Windows command-line file scanner. It runs only when I tell it to run. McAfee provides almost daily virus database updates on their FTP site.