hidden subliminal message in my browser

Hi there,
I am becoming crazy with a subliminal tune with a word that was secretly installed in my browser or computer and it is activated every some time. I am sure it came with some of the items I downloaded a couple months ago, but I can’t find where the **** is the script, addon, plugin, or whatever it is. May someone help me to find it? I have reviewed the Firefox file and reset it, I have checked in the registry, and the programs. I don’t know where to look forward!
Thanks for your help.