Shopping sidekick plugin plugin is advertising on my youtube,facebook and 4chan. How can i remove it?

[Harry]

I think this all started when i installed EZVID or something from that 'Company' of free Downloads and stuff and it forced a homepage onto my Firefox, Google chrome and internet, Although i only use Firefox.it wouldn't delete so i restored my laptop, all the nastiness left except fake Advertisements everywhere like Hot Girls in your area and win an I pad mini and it makes its way to my Facebook homepage,the top of YouTube and also on this website, as I'm typing, i have a fake woman trying to seduce me. i have tried everything from going on a program called autorun http://www.onlinethreatalerts.com/articl...hijackers/ and finally looking at the features and programmes on my laptops control panel and deleting downloadable nastiness. i have asked this before and just may resort to sending my laptop to PC world for a checkup but if i can do anything else just by myself to resolve such a horrible plugin, i would be grateful for your help!