Even when a client allocates space for an entire file, it has to depend on the OS for where and in how many pieces. A badly fragmented drive just reeks of entropy if there's a lot of file addition and deletion activity.
One thing I've found amusing is that in win9X, win2K, winXP - whether commercial, or MSDN, or OEM .... I've found that any iniitial install invariably needs a defrag right off the bat. The damned installer OS CD splatters system file chunks all over the disk.
My working machine (as opposed to my gaming machine) has several disks. I try to keep "things Windows" on the boot drive and as little else as possible. A second disk holds most of the applications, a third for data (like torrent files), and a fourth just because, um, its just nice to have an extra place for cleaning and emergencies. I also try to make sure each disk keeps about 20% spare.
If you're really careful, you can probably get away with defragging a few times a year... as always YMMV. Of course, if you run it as a background automatically scheduled process none of this matters.
Welll.... "super quick" is only true if you're Joe Sixpack "whats defrag" --- when I maintenance the occasional neighbor, a defrag usually has a substantial effect (especially after I delete all the crap AOL multiple installations and open up some space on the drive so it can even BE defragged). Cleaning the registry is certainly very good.... I *hate* looking at the registry and seeing what crap gets put in there.... actually I hate the registry concept except for OS purposes. Apps should keep everything in their folder.
