You will have more control with LW 4. It has more functions. Get LW 4.18 from the link at top of my post above.
Go to LW 4's menu bar, Tools -> Options -> Sharing, Basic - disable 'Share Finished downloads' option. Then next sub-tab down, Sharing-Advanced, disable 'Partial File Sharing'. Disable share torrents. I do not recommend using LW for torrents, instead use Vuse or uTorrent.
oh .. and Tools -> Options -> Sharing, remove any shared folders you see in that window. By default it will have something like C:\Documents & Settings\username\My Documents\LimeWire\Shared. Only disadvantage with dropping that folder is won't be able to use media player lol

No biggie, LW's player is not the best anyway.
To be sure, Tools -> Options -> Uploads & zero everything in speed & slots tabs.