incomplete folder represents both partial files & cancelled files.
Check under LW's menu bar, Tools -> Options -> Saving, & see how many days are set for keeping the incomplete files. If any of those files have past their age then LW will have removed their download history from the download preferences file, thus not be of any use.
Also, if the incomplete file is quite old, then in any case resuming it would be quite hard.
What you will find is LW is slow to open compared to before.
Some incomplete files such as 'some' video formats reserve space on the hard disk drive. For example, a 680 MB video file might automatically take up that much space in the incomplete folder as soon as you choose to start downloading it.
Just a hint, if you see someone with lots of files you want, do not download too many at once. Too many hits on their client will automatically ban you from downloading from them for that session.
Not sure if you can see the following image, but 'banned greedy servent' is what I see sometimes when the person has tried to download a large number of my files all at once:
Provided a different image any way. In this case, the person was already downloading from me, but chose too many more:
