Formatting a hard drive for Windows will be discussed in another article. In this guide I will show you how you can properly format/reformat a hard drive for Mac OS. Before you can use it though, you need to properly format or reformat a hard drive so that it will become compatible or readable with the Operating System that you are using. Published on October 20th, 2013 How to properly Format/Reformat a hard drive for Mac OSĪ hard drive or hard disk can be used in any type of computer, whether for PC (Windows) or for Mac.