Within the thread that I linked to, did you see this:Fixes for LimeWire ?

It's a good guide to deleting the preferences folder in both the old and new locations. Screenshots included.

When deleting the preferences folder, you delete the entire folder. If you also have a preferences folder in the new location of C:\Documents and Settings\your username\Application Data\LimeWire you'll see that I've given pretty basic instructions for deleting that.