For windows, close LW, then go to Start menu>Programs>Limewire>Uninstall. This will uninstall the program & its folder.
The LW save & incomplete folders are stored here by default: C:\Documents and Settings\"your account name"\Shared
To delete the LW prefs folder see: instructions here:
Fixes for Limewire
For mac osx, just drag & drop the LW program folder into the trash.