Perhaps someone else can give an easier suggestion. I'd compare the list on the dwnlds/search window to the incomplete folder listed in the LW Library window. Those that aren't on the dwnld list on the Dwnld window I would then delete. It can be a bit tediousome doing it that way though. And you need to be VERY CAREFUL not to delete the wrong ones!!! Ver careful!

Sometimes it canbe done by going directly to the incomplete folder & deleting those that are older than a certain date (whilst LW is closed!) But again you'd need to be sure of your choices.