Argh Winfixer managed to pop-up automatically, whenever I start firefox. It didn't even ask me to install, it just did it, luckily when I installed Ad-Block it seemed sort it out .
Somehow these Ads are managing to find a loophole through Firefox Anti-Pop-up feature.
Don't install Winfixer, useless piece of software and it has a trojan. Search for winfixer popup on Google.
Highly recommend that you run Ad-Aware, Spybot, Ewido Security Suite and MS Antispyware.