Sounds like you may have become infected. Try this
AVG(free) might be able to fix it. Be sure to update it before you scan your computer:
AVG Free Advisor: AVG Anti-Virus Free, then follow the prompts.
Once AVG has fixed the Problem you can delete it if you want to. AVG seems to catch problems other AV's don't catch.
Then go to Start > All Programs > LW > Uninstall, If you still have an uninstaller. If not
Go to Start > Search > type in limewire and search All Files and Folders.
Now if search finds anything LW related Delete Everything that It finds.
Now Download
Crap Cleaner which will clean your Registry and also clean a ton of Junk from your system.
Hope this Helps