Uncleaned tracking files

When I scan my computer, either quick scan or full scan, the following files are NEVER

eliminated:

        207.net; atdmt.com; realmedia.com; advertising.com; casalmedia.com; nextag.com;

         and orphan cleanup and sometimes doubleclick.com

I know these are tracking files, and wonder if they're part of the Symantec package, or

just viruses that can't be eliminated......or have they embedded themselves to track the

Norton software and reinstall as soon as the scan is finished?