Norton is your problem. Uninstall by going to Start --> Control Panel -->Add/Remove Programs
If you have any trouble removing Norton, use this Norton Removal Tool.
Yes...there is actually a tool to remove Norton. That's how bad it has become.
Now, after it has been removed, go back into Start --> Run type msconfig and press enter. Go back to the Startup tab and enable EVERYTHING (check them all)
Now restart your computer and see how it is. Even if it is fine, we still have to get you an anti-virus again.
Let me know how it goes.