First off, if a computer is running slow I lean toward sypware or even a virus. Second, Norton is know to be a resource hog so I would uninstall that and just install AVG free. Yes it’s free www.free.grisoft.com
Try using Spybot and scan for spyware or malware. Use the “msconfig” utility to stop any services that don’t need to run in the background such as AOL messaging or Microsoft instant messenger. Try disabling one thing at a time then restarting. If it messes something up then just renable it.
Hope this get it running a little better.
I believe that your computer system has been infected with some malicious software programs trying to invade and paralyze your entire system. You have to create a backup of your files before the problem gets worst. After backing up your important files, reformat and reinstall the operating system to clear all malicious software and errors in your system.