Disable Javascript and then check if there's a positive impact on performance.
I had Javascript disabled for about an hour. I'm on a public computer at the Library so I had to turn it back on or the next poor sucker who uses this machine will think the whole Internet has stopped working.
I didn't notice any particular change in performance.
The machine I'm using today is running Windows 7. At another branch I've used one running XP Professional. I always use Internet Explorer. This one is version 10. No other browsers are available on this machine.