Well, usually it should work when you change the saved file location to the same place as the incomplete folder isa and then press "Apply" before "OK".
Afterwards I reckon you closing LW completely (i.e also in the system tray) and then delete the LW preference folder (you'll have to go through the configuration screen once again when you start up LW).
With the 4.12. LW version the folder is called "LimeWire" an is in the hidden Application Data folder under C:\Documents and Settings\Administrator.<your computer name>\LimeWire