Do you mean that LW's not in your Start > All Programs, or is it not in your Program Files?
If LW's still there when you go Start > All Programs, then highlight LimeWire > LimeWire Pro > right click > send to > desktop.
If LW's not within Start > All Programs then go My Computer > C drive > Program Files > LimeWire > find the icon called LimeWireLLC (~140 KB in size) > right click on that icon > send to > desktop.
If you have no LW within Program files then maybe LW has been accidentally deleted