You'll have a .limewire preferences folder if you've used much older versions of LW in the past. If you've only used recent versions, you won't have one...the prefs folder will be in a different location.

Try looking for the preferences folder here (XP): C:\Documents and Settings\your username\Application Data\LimeWire. Application Data's hidden by default, so you'll need to show hidden files & folders in order to see it.
Control Panel > Folder Options > click on the View tab > check the radio button to ‘show hidden files and folders’ > apply > ok.

If you're a Vista user, try looking for your preferences folder in C:\Users\your username\AppData\Roaming\LimeWire
And more info about how to show hidden files & folders, and how to find the preferences folder here: LimeWire Pref Folder in Vista