What can I turn off to help speed up performance ?

Someone gave me an old Packard Bell 955, 333 mhz, 78 ram,    I want to put this computer in my garage so I can view online repair websites while working on my car.  I know it's a dinosaur but it was free and I don't want my good computer in the garage.  First thing I did was install Win XP and updated to most current updates and service pack 3.  I then install Norton internet Security 18.6.0.29.  This completely PARALYZED the computer making the simplest click of the mouse taking 5 to 10 minutes for the computer to complete.  I only want to access the internet with this computer,  no email or anything like that.  What can I turn off to help speed or is there a scaled down version of antivirus I can use.  Also when I turn something off I keep getting badgered about how I need to turn it back on,  how to turn off messages ?

 

Thanks