To resolve the possible two screens running in the background you might want to make sure you only have one webpage designated as your homepage. Go to the webpage you would like to have as your homepage, then click on the down arrow attached to the house icon on your toolbar. From the dropdown list select 'add or change home page'.
Disabling any unecessary Add-ons may help increase the speed of IE8. The following Microsoft Support website can help you to do this:
http://blogs.msdn.com/ie/archive/2006/07/25/678113.aspx
If you are still having problems then I recommend to try and reinstall IE8.
Hope this helps. Good luck!
Melissa
IE8 Outreach Team