There is ads all over my computer?

Oh, gosh. They are ruining my life. I bought this computer almost a year ago. Brand spanking new from Best Buy. I loved it. It was fast, no ads, I could do anything. A few months ago I was looking for a program for photo editing for a website I was making for a friend. I downloaded one and my computer had a spaz attack. I deleted it instantly and ran my virus scan (which was from Best Buy) and it said that there was two threats removed. I was thinking it was a close call. Ever since then I have ads like crazy! I'm not talking about the usual ads you have on the side bar on websites like Facebook. I'm talking where when I go onto a new site and click, another tab pops up about taking a survey or something. All the time.

I can't go on Youtube anymore. On the side where they show videos, every third video there is an ad, they talk, play music, etc. They are always changing, which makes the page constantly loading, making it slow. I try muting the ads, but they just change to another one. They also have these ads on websites, such as: Craigslist, Wiki, Yahoo, etc. I run my virus scan religiously (It's Webroot by the way) and it says there is no threats, but there is still ads. Oh, the ads say they are not from that site. So I guess I have either a virus or spyware.

Question is, what do I do to remove it? When I bought this computer I bought a year warranty for coverage like water damage, drops, one replacement battery, etc. It's up this month. Do you think if I bring it in they can remove this? I thought a virus scan would PREVENT things like this! If they won't, what else can I do to fix this? I've only seen this once before on my mom's laptop and it eventually crashed. I don't want that as I use this computer for my online school. Please help? Thanks!