Another hard disk condition that can adversely affect performance is when the volume becomes overly fragmented. Let's take the example used in a previous chunk: you have a file stored in "storage box" 11, and boxes 12-18, 23-25, and 59-67, as well. Figure 4-17 helps you visualize how such a file would be stored.
Figure 4-17. A fragmented file takes longer to retrieve.
Wouldn't it be faster for Windows to retrieve the file if it were in boxes 11-29 instead?
Of course. Disk fragmentation occurs when contiguous file storage is not possible, and it is an unavoidable result of long-term computer use. When files are removed from your computer's disk, they can leave large gaps that could otherwise be used by other files. So even though there's plenty of space on your hard disk after a mass deletion, your hard disk still may not be operating at peak efficiency. It may need to be defragmented.
Here's how to defragment your hard disk:
The utility looks for fragmented files, like the hypothetical file from this chunk's introduction, and rearranges them in areas of contiguous space if possible. Note also that defragmentation is done on a volume-by-volume basis, not on an entire hard disk.
You can defragment in the background while working at the computer, but you might want to think twice before you do. Because it can take such a long time, and because the disk will be running at maximum capacity, it will really slow down normal operation. You might want to defragment when you're able to leave the computer for several hours, such as when leaving the office for the day, as I'm about to do right now.