Can you open Internet explorer and click Tools then Internet Options.
Look in the home page box at the top of the window that opens and make sure only one address is entered, If there are two addresses entered simply delete one then click OK and close IE.
Wait about 5 seconds and open it back up.
Let us know what happens.
So there is only http://www.yahoo.com only, It is not in there twice is that correct?
Is it loading two seperate pages on two seperate tabs or is it the same page twice in the same window, One above the other?