It’s easy to lose track of how many add-ons you’re running in IE8 and how they can slow things down. An interesting experiment is to use the “-extoff” flag to disable all add-ons and see how zippy IE8 becomes.
To do this, create an icon for IE on your desktop (usually "C:\Program Files\Internet Explorer\iexplore.exe") and add “ –extoff” to the end of the command. So, if you’ve installed IE8 in the default location, the target/location would become:
"C:\Program Files\Internet Explorer\iexplore.exe" –extoff
Try surfing a few sites (you’ll be warned you’re running with extensions off). When I did this the speed increase was noticeable, suggesting that add-ons were having a reasonably significant effect on my browser speed.
To get an idea of which add-ons are slowing you down the most, go to "Tools” then “Manage Add-Ons” then, ensuring “Toolbars and Extensions” is selected, scroll right so you can see the “Load Time” column. Try removing any add-ons that a) aren’t particularly useful and b) have long load times.