[wharfrat73]

http://www.utorrent.com/faq.php#How_...the_torrent.3F

There is little use to pre-allocate except for making sure you have enough space when starting a torrent. It does NOT reduce fragmentation as compared to not using it, since µTorrent ALWAYS allocates the full file when writing to prevent fragmentation, regardless of if pre-allocate is on (unless you use compact storage or sparse files).

http://azureus.sourceforge.net/faq.php#13

Incremental File Creation: only stores the file size. Allocation occurs as the files are downloaded. Results in a much more fragmented file.