1. Go to Start menu > Programs > LimeWire > Uninstall.
2. Run this utility:
Crap Cleaner (which will clean the registry)
3. Install using the OFFLINE version of LW:
http://www9.limewire.com/download/LimeWireWin-full.exe
* BTW if you are using VISTA, then you will need to set the installer to Administrator.