Ive Got A Serious Computer Problem. Can Someone Help?

Ok well we just got internet a few days ago. After about 3 days we got this stupid adware/scareware thing pop up. We didnt have any antivirus stuff so i had to create new user accts. We didn’t use the computer for 2 days after that. Then we got this McAfee Internet Security 2010. We uploaded the software and thought everything was fine. Well now we got this stupid Security Tool scareware crap and I though we were protected. Ive got no clue how to get rid of it and why our McAfee isn’t guarding against it. Heck it doesn’t even see it as a threat. Ive scanned and it doesn’t come up with anything wrong. It says we have a 30-day free phone support and unlimited email and chat assistance, but when i go online for it, it says i have to pay. Wtf? Plus ive looked up other questions on the Security Tool Virus and all they can say is to download something that will scan for it. When i do, the “software” they suggested will only scan but wont remove. I don’t want to have to download something that will get rid of this if i have to pay for it. I want this stupid McAfee thing to work. So what the heck do i do?