I think I have a virus what now?

I think my computer has a virus. I don't know how it got there because I was away and I'm the only one that uses the computer. I never installed anything to the computer. It started all of this very spontaneously yesterday when just all of a sudden all of these popups kept popping up making it impossible to use my computer. I turned it off and back on and then the background only says restore active desktop. Now when Ill be on a website when I click on a link it goes to a random search website or goes to a website that is called dnserror.org. I also have a lot of popups compared to before. My dad thinks that its a conspiracy for companies to make money off of you and blames Mcaffee for it since they had a thing that popped up to renew my stuff. I don't have the money to buy any antivirus software and he doesn't believe viruses exist. How do I get rid of this and is there any legit free antivirus software out there?

I think I have a virus what now?computers

You have one or more Trojans:

Download SuperAntiSpyware. It will remove the majority of difficult Trojans etc.

http://www.superantispyware.com/

Turn off System Restore. Load the application in normal mode but run in Safe Mode. Safe Mode can be started by continually pressing F8 during the boot sequence.

If you are badly infected you might need to run SuperAntiSpyware more than once to give you a totally clean system.