It's worth checking that there are no extensions causing it to run slowly. You can either use Run in the start menu to type " iexplore -extoff ", or right click the link to Internet Explorer, go to properties, and add the -extoff to the end of the 'shortcut target'.
If Explorer runs smoothly after that, it's worth running through your extensions to remove ones you don't need, removing and adding the -extoff command to test after each removal.
Failing that, I'd recommend opening Explorer, going to Tools > Internet Options > Advanced and hitting reset. Bear in mind though, that this will reset all of your settings in Explorer, including clearing the history and any saved passwords and toolbars, etc...
I had ongoing issues with IExplore, mostly with the cache, and ended up trying alternative browsers until I found one that worked well for me.