First, update to Firefox 13.0.1 (the latest Firefox as of today).

After you do that, you can easily change your search engine default by reading Search bar - add, change and manage search engines on Firefox

Users probably more often want to know how to reset Firefox after unwanted toolbars have mucked things up.

The home page itself may be set to almost any page or list of pages that you want. You then have the option to set it to display at startup or not. The chosen page or pages may still be obtained after startup by clicking on the home icon.

• see the article how to set the home page

Because the standard homepage has now has additional controls on the lower edge a solution may be to set the homepage to include that by entering in the list about:home then to enter a second page such as bing add the pipe symbol | and the address of bing. (You can also set pages with drag and drop methods)

Something else worth knowing is that Firefox has a search bar, usually displayed top right by default. That will by default use Google and have a list of a few alternatives. It is possible to add almost any search engine in a variety of languages to that listing, and set any one of them as the one displaying. See the article

• Search bar - add, change and manage search engines on Firefox

As you have already asked a very similar question that already has replies I hope you do not mind if I lock this thread on our forum. Please continue at https://support.mozilla.org/en-US/questions/930189