Limewire will only resume files, that were saved in downloads.dat, since swarming requires LimeWire to know which parts of the file it already downloaded, so LimeWire will save a map of each file in downloads.dat.

Recreating a map of incomplete files is not easy.

If LimeWire crashes (or if it is killed) while the downloads.dat is written, the file could be corrupted and LimeWire can't resume any files. (So when LimeWire doesn't react anymore, first thing to do is, create a backup of downloads.dat, before killing the process).

The downloads.dat file is written every 30 seconds and when LimeWire is closed.