get rid of Norton. It is not doing anything anyway.
Remove it and check for any improvement.
I also wonder if you are a recent mover from a Windows computer or if you use a Windows computer at work.
In both those cases, I find that the user uses the Red dot at the top of a window to close out the application they are working in.
The belief is that if it works like that in Windows, it should work like that on a Mac. It doesn't.
Check under the icons in the dock. Any that have a white or black mark underneath them are applications that are still running, even though there are no windows open, and are sucking up your memory.
A quick way to find running apps is to hold down the Command + Option keys and then press Escape (Esc)
This brings up a list of running apps.
Give it a try
That 800Mhz speed in your system specs is the memory speed and not the speed of your processor.