I have a brand new pc and it has been hit with a porn virus?

I got a brand new computer for Christmas and I have been hit with some kind of virus. I am not that great with computers so I am not sure what or when this has happened. When I am on the internet is constantly pops up and tells me I have an unknown trojan and then wants me to download the "newest virus protection". I have norton and windows defender so I didn't down load anything else. Plus when I try to do a search for something on yahoo it pops up and says my browser has been hijacked. I don't know what any of this means or what to do, so if any of you can help me, please break it down kindergarten style. Oh, and sometimes when I click on something porn pops up and I don't look at that crap and really want this off my computer. Please help.

I have a brand new pc and it has been hit with a porn virus?anti virus software

run this free tool to remove it. http://www.bleepingcomputer.com/files/sm... good luck.

I have a brand new pc and it has been hit with a porn virus?aurora

Things keep poping up mean u are infected!,

May you please try Lavasoft Ad-aware,

http://www.download.com/Ad-Aware-2007/30...

Update it befor running then do a full system scan,clean all infections.