Have you ever installed any software that could make your computer behave like a DVR (like TiVo) either for video or for music?

Next time this happens, can you stop the sound by closing all Firefox windows?

If it doesn't stop, could you check the Windows Task Manager to make sure Firefox is fully shut down? Press Ctrl+Alt+Esc, then click the Processes tab, then look for both of these and use End Process to unload them:

• plugin-container.exe
• firefox.exe

If it then stops, one of your Firefox add-ons might be to blame. You can review and disable all nonessential add-ons here:

orange Firefox button or classic Tools menu > Add-ons

Check both the Plugins and Extensions categories.

If it still doesn't stop when Firefox is completely unloaded, Firefox might not be involved. Can you think of any other software you installed recently?

You can also check these for the disabled XULRunner 1.9.1 extension (considered malware) in your system details list.

• [/questions/743526]
• [/questions/749007]

Do a malware check with some malware scanning programs on the Windows computer.
You need to scan with all programs because each program detects different malware.
Make sure that you update each program to get the latest version of their databases before doing a scan.

• http://www.malwarebytes.org/mbam.php - Malwarebytes' Anti-Malware
• http://www.superantispyware.com/ - SuperAntispyware
• http://www.microsoft.com/security/scanner/en-us/default.aspx - Microsoft Safety Scanner
• http://www.microsoft.com/windows/products/winfamily/defender/default.mspx - Windows Defender: Home Page
• http://www.safer-networking.org/en/index.html - Spybot Search & Destroy

You can also do a check for a rootkit infection with TDSSKiller.

• http://support.kaspersky.com/viruses/solutions?qid=208280684

See also:

• "Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked