Hi Charles, since the Firefox settings you posted look clean, could I suggest posting on a specialized malware cleanup forum? They can advise on the use of tools that require step-by-step assistance. There are some recommendations in our support article: Troubleshoot Firefox issues caused by malware.

Note: those programs and forums are free. If you search for SurfVox in Google, you will find numerous services that can sell you phone support or software tools. Some of those might be faster, but I think it's worth trying the free ones first, particularly because the forum discussions are held in public so the advisors know people are monitoring what's happening, and you do not need to give strangers remote access into your computer where they might clear/delete things important to you.

I'll add few thoughts based on my searching:

(1) Did you check the Windows Control Panel, Uninstall a program, for anything installed around the same time? Click the "Installed on" column heading to group installs by date. This can be helpful in spotting bundle items with innocuous names that you might not notice when sorting by name.

(2) On Google's forums, the bad software was discovered in a folder named "soundmng" which was under the hidden AppData path. To drill down to that folder, you can turn off the hiding of hidden files and folders using the steps in this Microsoft support article: http://windows.microsoft.com/en-us/windows/show-hidden-files

(3) Going forward, I suggest a general policy never to install codecs except from Microsoft or the site where you got the relevant video player (e.g., Adobe for Flash, Apple for QuickTime).