Changing the download location will have moved all the incomplete files over to the new incomplete folder. So should just be a simple matter of changing the location back in your options. Unfortunately LW 5 does not have a default button like LW 4 had.

If you reinstall LW, you will find your downloads go to same location as they are now. You'd need to delete your LW preferences.

Why not explore your folders, you will probably find a LimeWire folder next to the incomplete folder, open it .. is Saved inside or another folder used for downloading. Once you know this you can change location.