How did I get ads? And how to take them off?

[Ginny]

Okay so I got rid of it and it took me about a few months to get rid of those annoying stupid ads. They annoy me so much. Today I finally got rid of them and was so happy that everything was working faster than what it was before. I don't know what I did, I remember deleting a few instalations sicne I didn't need them a they didn't work then shutting down my computar but thats it. When I got on today there was no pop ups and disgusting photos on the blank spaceson the enterent. Then I clicked on YouTube to show a question that is a spam or whatever than a pop up came. I was praying and praying that it was just one thing then it wasn't and they all came. I hate it since I wont show my little brother anything on YouTube because of the pictures that come up. Please I want to know how to get rid of them AGAIN. They are anoying as anything. And can you tell me how I got them anyway? Please I have tried everything!
Mine is a Windows computar and I don't want to download anything I have Norton installed already

[James]

You got them because you downloaded something and did not look at the ticked boxes.

How to get rid of them:
you need something like Norton Antivirus Software because the adds are viruses.
Norton may not be cheep but you can get a free trial: http://au.norton.com/downloads-trial-norton-antivirus/

other software works two but i think Norton is the best.