You most likely downloaded a Virus the link below should help. You need to educate your self before you do any more downloading. There are allot of viruses on the Gnutella network. LimeWire has nothing to do with the problem you are having. If you can not get rid of the virus yourself there is a link to Norbies world in the link below. He will be able to help you get rid of it.
http://www.gnutellaforums.com/showthread.php?t=41432