Look for this folder C:\Users\your username\AppData\Roaming\LimeWire. The folder named LimeWire is the preferences folder.

Don't forget that you have to show hidden files & folders first. Did you look at this thread? It shows you how to show hidden files & folders, and how to find the preferences folder.
http://www.gnutellaforums.com/genera...der-vista.html
After that folder's deleted, start LW & see whether it connects.

If deleting the prefs doesn't fix things, you could also look at the advice here about replacing the gnutella.net file.
http://www.gnutellaforums.com/connec...t-fix-try.html
That refers to Win XP, but it'll give you the general idea You'll need to open your preferences folder (named LimeWire, the same one that you deleted before) & replace the gnutella.net file which lives inside the folder named LimeWire.

Remember that when deleting preferences or replacing files within the preferences folder, LW must be properly closed.