You can disable or remove most toolbars here:

orange Firefox button or Tools menu > Add-ons

On the left side, click Extensions. Then read down the list. Usually the active ones are listed first, then the inactive ones.

If the add-on can't be removed there, you may have to go to the Windows Add/Remove Programs control panel.

Any luck?

Thank you so very much for your answer. I went into Tools menu, add ons, etc., etc., etc. and deleted the Yahoo tool bar - yes it worked. Thank you again.

Once again, I thank both of you for your support and accurate replies.

I have Avast Anti Virus and I just upgraded and downloaded Mozilla Firefox 5.0. It stated that Avast is enabled ????? Does that mean I'm not protected anymore ???