Browsing very slow

My pc has started taking an age to open certain web pages I tried going back to IE7 from IE8 but made no difference.I have also noticed that when there is a pic on the page It opens in stages very slowly .I am using Nod32,Comdo and Spysweeper.I have scanned my PC and nothing is showing up.Is there any setting I can adjust to speed things up or Is there something my AV & antispyware have missed?
This prob Is also when I use Firefox.I am using Virgin cable 20MB connection so I shouldnt have to wait for pages to open?Could there be a problem with the memory/