Directory is here: C:/Documents And Settings/your_username/.limewire
And you delete the entire folder not just the contents. Simple just send the entire folder to the recycle bin (but only with LW closed.) Next time you open LW it will create a new preferences folder. So make any note of settings before you delete it as you'll need to reset them upon re-opening LW.

Oh I forgot the above is for Win Xp.

Windows 98 / ME: Your .limewire folder is in "C:\My Documents"
Windows NT 4.0 / 2000 / XP: Your .limewire folder is in "C:\Documents and Settings\Username"