...
oke,
a hd exist in perfectly placed clusters, you create a file and it know which cluster to grab to provide the most integer file possible. The speed and processing when making this file depends on whether the system can find the right cluster rightaway, if not it will fetch an alternative but not the best ( opposed to defragged where its fast because all clusters are placed in the right order ). However, when you delete a file it will just spread out those cluster all over the available spaces left on the hd so the next time the system need to make a file it will take longer before creating the file and its not the most ideal condition( so if its a system file being made it will reduce the system's integrity.
Now im talking one file, but all you leeching mofo's are talking about either full dvd porn (4.1Gb), warez or the core stuff....audiotracks ( a 100mb in the least a track, average 8 tracks per song). So these are a lot of clusters being made and dropped/spread back over the disk, grabbed again, spread again over and over and over and over untill you defrag and sort clusters back into the right order. When you know you're handling large files then defrag regulary because it affects performance on your daw (when you record a track...it takes those clusters again) so the chances that your recordings corrupt are bigger and reading/writing goes slower (this also includes gui's and menu build up).