Well, since you do not seem to consider buying a bigger HDD (an external maybe), ther is not much what you can do. One thing would be cleaning you pc with CCleaner (
http://www.ccleaner.com/download/), which will surely free some disk space.
Another thing you could do is to calculate first how much disk space you've available and then download only that amount, if necessary one file at a time. LW seems to reserve the diskspace for files put in the download section.
