As I’ve explained in a previous article, defragging rarely gets you to a 100% completely defragmented machine. There are a couple of different reasons why, but I’ll leave it to that article to cover that situation. The real question here is: does defragging too often harm the machine?
Absolutely not. Let’s talk about why.
Help or harm?
From the hardware’s perspective, defragging is just another way to access the hard disk – which is almost constantly in use anyway. Quite literally, to the hard disk it simply “looks like” a program reading and writing information from and to the drive.
Defragging often doesn’t harm the drive – it’s just as if the disk were being used heavily by any application – but in the end, it may not really help that much.
Once you get to a point of being relatively defragmented, then the additional work of defragging further just isn’t worth it. As soon as you get “pretty good” defragmentation, say in that 5% range1, then your machine is going to be essentially as fast as it would if it had been perfectly defragged.
I do recommend that you defrag periodically. Windows 7 does it automatically for you once a week. That’s a fine interval if you’re setting things up for yourself.
What defragmenting does
Defragmenting will not make your computer slower. It’s point is just the opposite: it’s arranging files on the hard drive to be more efficient.
Defragmenting also won’t harm your applications. Applications don’t even know about fragmentation.
If you open an application and you access a file, the application accesses the operating system which locates the file on the hard disk. If the hard drive is defragmented the amount of time it takes for the operating system to find and load the file might be quicker than if the drive were heavily fragmented. That’s the only thing an application might “notice”.