Oh dear not good....You have a virus..
The only AV that I know of to get rid of this virus is AVG, it is free...So if you aren't running that AV the best thing to do is disable the one you have and download AVG, scan your computer, get rid of the virus and then you can uninstall AVG and make your normal AV active again...
AVG download.....
http://free.grisoft.com/doc/2/lng/us/tpl/v5