Keep getting redirected

Ok, so I was trying to watch an episode of a show I missed, something came up and said I needed a codec and I clicked (STUPID, Yes, I am, I know...). Nothing came out though and I don't recall actually typing in my administrative password. So now, Safari and Firefox will redirect me whenever I search for something on a search engine. I get redirected to a weird site that has similar search results. Also, sometimes when I type in an address on the address bar it will take me somewhere else. I looked up a bunch of stuff online about this and it sounds like that DNSchanger trojan. The places I read that spoke about this said you can see if you're 'infected' by doing certain things, like looking to see if there's a specific file on your Internet Pluggins folder, or looking up crontabs on Terminal, as well as checking your DNS on the Network Preferences of AirPort. HOWEVER, every time I search for this, there's nothing there, in any of them. No crontabs, no weird thing on DNS, no 'pluggins.settings' on my Internet Pluggins folder...nothing. I have Norton Internet Security and though I ran it various times and it found/deleted 'trojans' and a 'zango adware' thing, Safari keeps doing this whole redirect thing every time I search or every once in a while when I type something in the address bar. It's super annoying and I don't know what to do and if this is affecting my computer somehow or damaging it in a way I don't know and can't see. I'm not sure if this question was answered before, though I did try to look before I posted. I could only find a thread about it being highjacked but the user's problem was solved fairly quickly and the advice given was of no use to me. I'd really REALLY appreciate the help. Thanks.