That's usually a worm....read here:
http://www.gnutellaforums.com/showthread.php?t=41432
If the suggestions made in this thread do not solve your problem, try to open your task manager (crlt&alt + delete -one time), there you go to processes and look for a limewire.exe process. If found force it to end.
Then use the search function of your computer to look for any remaining LW files using the search query "limewire". Delete all those file found.
Then open your regedit via Run...>Regedit. Go to local machines and look for the Limewire folder. Delete it.
That should it be...
Cheers
