How to stop this site: http://thecoolpics.com/ details below?

I've been given an address by a friend, and I've opened it.. Then suddenly, my computer began to slow up and after the slow up, I've discovered malfunctions in setting up the homepage, and my yahoo messenger became unstoppable and once in a while, sends funny messages to all of my contacts like "never click into the links like something in this image http://thecoolpics.com/dontclick.jpg !!! " or "hot pics this week http://thecoolpics.com/hot.jpg" and displays my status messages linked to this funny messages. So my senses tells me to restart, and after I restarted it, I opened my Internet Explorer then it displays the site with the address ' http://thecoolpics.com/" I wanted to reset my homepage to yahoo, but it was colored grey, and every time i open my Internet Explorer and this site appears, a trojan was said to be deleted by my anti-virus. How can I delete this annoying thing that's irritating me while using the internet?