Safe and Secure
It may send shivers down your spine, but hard drives fail.
They do more than fail: they lose files, get corrupted, become unreadable, and all of the things we users dread when we go to start our computers up in the morning.
For example, if you pull the power cord out of your PC while you're writing files to the hard drive, there's a tiny chance that you might lose a file - or that the hard drive may become unusable.
Even copying or moving files from one location on a drive to another can cause problems if the drive is flaky, or if there's a power surge or power failure.
That's a roundabout way to introduce the topic of Defraggler and safety. You may wonder if Defraggler is safe. After all, it has access to your entire hard drive, and spends its time moving thousands of files around to optimize and speed up your PC.
The simple answer is: Yes.
Windows has a set of built-in procedures it uses whenever you copy or move files on your computer. For example, if you move a file from your hard drive to an external USB drive, it will copy the file to the USB drive first, then delete it from the hard drive. In case a problem occurs writing the file to the USB drive, it still has the original on the hard drive to work with.
That's a simple example. Windows has many safeguards to prevent data loss when working with files. The good news is that Defraggler uses those same safeguards.
When Defraggler reads or writes a file, it uses the exact same techniques that Windows uses. Using Defraggler is just as safe for your files as using Windows.