Shepbob..
IF you have Malwarebytes' Anti-Malware (v1.60 or later) installed but it won't run, first try the following. Malware may (or may not) be why it won't to run.
• Navigate to the Malwarebytes' Anti-Malware (MBAM) folder in your Program Files. C:\Program Files\Malwarebytes' Anti-Malware
• Within the folder you will see a Chameleon folder. Open it and double-click on firefox.com.
• As instructed, press any key. Do so quickly when the command prompt opens.
• MBAM will begin to update. When the update process is complete, click OK
• When the MBAM terminates threats running in memory, it will automatically open and perform a scan.
• When the scan completes, click on Show Results. Click on Remove Selected to remove the threats found.
• Click Yes in order to restart your computer and complete the removal process.
If the above doesn't work, see if Malwarebytes' Clean Up Utility (direct link) will allow you to remove it.
Best of luck..
Carol