|Scan with Malwarebytes to be sure.|
Turn off many processes from starting with Windows by running msconfig, going to the Start tab and unchecking all except MS and antivirus program., Apply and restart machine.
Norton does not always completely uninstall when removed the normal way, go to their website and download their uninstaller to completely remove traces that can prevent other AV programs from working properly. Try using Avast or Microsoft Security Essentials.
Use Process Explorer from Microsoft since it shows more about the processes running than Task Manager.
Uninstall programs you never or no longer use.
You have to be a little bit crazy to keep you from going insane.