My computer has slowed to a crawl and I can't figure why. Need help? See details below.?

I have tried every program in my Norton Systemworks. I found no spyware or virus'. I ran Superantispyware and found nothing. I ran Ad-Aware SE personal and again found nothing.I drfraged. I even tried Norton Go-Back.

Symptoms: when I turn on my computer it is extremely slow in loading Windows XP. It is extremely slow in downloading my desktop, and slow in moving around the internet and my programs.

My mouse is jumpy instead of smooth when moving around. My screen saver, Windows moving triangles is moves jerky and not smooth. After awhile my screen saver will feeze up and disappear. My screen goes blake and i can't get anything to come up and have to reboot my computer my manually turn it off and then back on.

Oh yea, when I intially get on the computer my Norton shows it is refeshing and this takes quite awhile to complete.

This is all a very recent problem. I am at my wits end. Would appreciate any help I can get.

Thank you, Fred

My computer has slowed to a crawl and I can't figure why. Need help? See details below.?live update

First thing to do is bring up the task manager and see which process is killing your performance. Right click your tool bar and select 'Task Manager' and then click on the processes tab. Look for any processes that are using a lot of CPU. You can then update this question with the process and maybe someone can shed some more light on the issue.