Problem with facebk and internet explorer

Hello,
i m having problem login to fb as well and worst of all, once i start up my comp, i can use the internet explorer, but in less than a min, i will have the error of connection problem. i was told that my comp most prob down with virus....
where can i download the virus killer? how i can confirm thats a virus?
i ran my spybot and avg but they did not prompt me of any virus detected....