Make sure your drive/partition you are downloading to has more than 25% of total capacity remaining, and use your defragmenter utility to be sure it is defragmented. Also check the drive with a proper utility to be sure there's no file/directory damage on that drive/partition. Downloading lots of files will easily fragment your drive so you do need to defragment on a regular basis. Also be sure you have plenty of space left on the drive. I would recommend using a drive/partition which does not include the system drive.