Use software called RegCleaner,there check for any entries with name/key Norton or Symantec,if u find any key remove them.
*www.worldstart.com/weekly-download/archives/reg-cleaner4.3.htm
Go to Start>Run,then type msconfig.
There in that panel,go to Startup tab and search for any Norton/Symantec related entries,if u find one uncheck it and save abd restart.
Check that if u have any Norton/Symantec files/folders in Program Files and Common Files folder,if there are then delete them.