The entire idea of Norton’s running when you start up is to provide [b]Real Time Virus Protection[/b] which is considered by everyone to be a good thing as it prevents infections from occurring most of the time.
The idea with any AV Program is to prevent the infection not to clean it up after the event and possible unrepairable damage is done to the [b]OS’s Critical Files or the User Accounts Files.[/b]
If Norton’s is running an AV Scan every time you start the computer you need to go into the Norton Settings and tell the computer when you want it to scan the system for Infections and stop it starting a scan every time that the computer is booted. It’s also possible depending on the version of Norton’s AV that you have never allowed a complete scan to finish so it’s attempting to do this every time that the computer is booted to make sure that it’s clean to begin with and to try to keep it that way.
This was written for Linux users but you may find some benefit in reading it as it will help you to get the answer that you need.