If you have not got a firewall or any antivirus software, get them. i'm sure someone will reccomend some if you haven't got. I use Norton, but it's six of one and half a dozen of the other as to which you go for.
this should help stop the kak arriving on your PC to start with. then use some form of adware removal software to get the stuff off the PC.
hijackthis and cwschredder are the two that seem most popular/effective.
click here for both. Not guranteed to work, but may well do.
Also try searching the help room archive, as many many useful links contained.