Do you mean that Bing is not just showing up as one of your many search engine choices but has forcibly taken over as your default search engine and/or your home page??

I'm a little concerned about this:

selena18 said

I upgraded Firefox and was careful that nothing else was selected with the download.

Because:

• When Firefox auto-updates, it doesn't give you multiple selections, it just updates the program
• When you install directly from Mozilla, there also is nothing to select or deselect

So I suspect you got some kind of unofficial bundle build that has inserted add-ons into Firefox and perhaps other unwanted things...

Here's my suggested procedure for tracking down and cleaning up bad add-ons and other hijackers. I know it seems long, but it's really not that bad.

(1) Open the Windows Control Panel, Uninstall a Program. After the list loads, click the "Installed on" column heading to group the infections, I mean, additions, by date. This can help in smoking out undisclosed bundle items that snuck in with some software you agreed to install. Be suspicious of everything you do not recognize/remember, as malware often uses important or innocent sounding names to discourage you from removing it. Take out as much trash as possible here.

(2) Open Firefox's Add-ons page using either:

• Ctrl+Shift+a
• "3-bar" menu button (or Tools menu) > Add-ons
• in the Windows "Run" dialog, type or paste
  firefox.exe "about:addons"

In the left column, click Plugins. Set nonessential and unrecognized plugins to "Never Activate".

In the left column, click Extensions. Then, if in doubt, disable (or Remove, if possible) unrecognized and unwanted extensions. All extensions are optional; none come with Firefox.

Often a link will appear above at least one disabled extension to restart Firefox. You can complete your work on the tab and click one of the links as the last step.

Any improvement?

(3) You can search for remaining issues with the scanning/cleaning tools listed in our support article: Troubleshoot Firefox issues caused by malware. These on-demand scanners are free and take considerable time to run. If they finish quickly and especially if they require payment, you may have a serious infection. I suggest the specialized forums listed in the article in that case.

I will continue with settings fixes in the next reply

To fix various settings after removing any bad add-ons:

(1) Home Page - please see either of these articles:

• Startup, home page, tabs, and download settings
• How to set the home page

Note: If your Firefox desktop shortcut loads a different page than the Home button or a new window (Ctrl+n):

Check that the shortcut is not hijacked. Here's how: right-click the shortcut > Properties > Shortcut tab. For Windows 7, your Target should be no more and no less than:

32-bit: "C:\Program Files\Mozilla Firefox\firefox.exe" 64-bit: "C:\Program Files (x86)\Mozilla Firefox\firefox.exe"

If there is anything following that, go ahead and delete it.

(2) Default search engine - please see:

Use the Search bar in Firefox and manage search engines

(3) If problem settings return when you exit Firefox and start it up again, you might have an unwanted user.js file. Please see this article for more information about that:

How to fix preferences that won't save

Note: By default, Windows hides the .js extension. To ensure that you can find and either rename or delete user.js, you may want to turn off that feature. This article has the steps: http://windows.microsoft.com/en-us/windows/show-hide-file-name-extensions

Does that cover it or do any issue remain?