If you got the same version as I did, go to Control panel, Add/remove programs, locate McAfee SiteAdvisor and you can uninstall it there.
I too dislike this version 28, it's just that in my case it forcibly installed IE components too crippling IE apparently in the process. I was using Firefox version btw.
🙂About the previous version, I have no idea

sad I too would like to get back my simple Firefox add-on.