Your incomplete folder will be in the same folder that your saved folder is in. In Limewire go to the saved folder in library select some file and press explore. If you're using Windows (just guessing since you didn't specify which OS you use) then you have accessed the saved folder in windows. Now close Limewire completely (Also in the system tray)

In the Windows folder, beside the forward and back arrows, there is a folder with an arrow pointing up. Press that and you enter the folder that both your saved folder and your incomplete folder are in.

Now drag the incomplete folder to the recycle bin

Then Startup Limewire and you have a new Incomplete folder