It typically depends on your usage activity. For example, if you’re a casual user who only installs a few programs and doesn’t save a lot of large files, then you should defragment your hard drive once every month or two. Those who are more intensive users with large file transfers, downloads and installations may need to defragment their hard drives more frequently, such as every week. If you find that your computer is running slow or an application is taking too long to launch, then it’s time to defragment your hard drive.