norton is generally veeery slow.
To find out what is slowing you, hit CTRL-Alt-Del and "Task Manager" button to watch the CPU 'speedometer.'
Choose "Processes" tab at top.
Click "CPU" column 2x to get the ranking from top to bottom ("System Idle Process" should be the highest CPU number most of the time.)
Watch to see what process ("Image Name" is hogging your CPU). You can leave Task Manager open and check it when the system is going particularly slow to figure out the cause.
When you suspect a process as the hog and can't figure out it's origin, google it and you'll get an answer.
It's good for checking out what's running behind the scenes, particularly if you suspect adware or a virus.
If only your IE web browser is going slow, go to Tools/Manage Add-Ons/Enable or Disable Add-Ons and scroll down to see what Add-ons are listed. You should be able to recognize most of them. If not, google them to see if they're not unwanted...
Next, I'll give you instructions to edit the Registry.