I recently downloaded Yahoo Messenger, and Yahoo ever so kindly

,implanted a toolbar on my internet screen which I cannot remove. It is interferring with my bottom tool bar (?) which will not pop up from it's auto hide position when I hold the mouse over it. I never had this problem before I got the Yahoo stuff.
1. How can I get rid of this Yahoo Toolbar?
2. Why does it interfere with my auto-hiding toolbar at the bottom of my screen?
All suggestions appreciated to get rid of this imposing pain in the neck.
Kermie