Yet another reason why Linux is better!

You don't have to defrag the hard drive. - Fragmentation and Unix file systems

More detailed explanation:

When you use a computer for a long time (months or years), the file system gets messy.  Just like your desk.  By de-fragmenting your hard drive, you clean it up again.  This accomplishes two things: your computer can find files faster, and you have more free space (just like real life!).

Windows uses two file systems: FAT and NTFS.  Linux uses pretty much any file system you want, but it prefers ext3.  Ext3 manages itself in order to avoid fragmentation.  Like a desk that keeps itself organized.  Pretty frigging cool.