macOS could not be installed, how-to fixįormat your new hard drive for macOS or OS X.How to create a macOS Catalina USB installer.Factory reset MacBook Air and other Macs with macOS.How to downgrade from macOS Mojave to macOS High Sierra.Or use the OS X installation disc that came with your machine - or buy a new one - to boot up and install OS X on your Mac’s hard drive.Download the relevant macOS or OS X installer from Apple, then use Terminal to create a USB installer you can boot up from.Install macOS or OS X from Internet Recovery Mode, which you can boot into by holding option+command+R while your Mac powers up.If you’re tech-savvy but don’t know where to start, use these Quick Tips to point you in the right direction for getting macOS or OS X on your drive: Simply follow the instructions below to install the latest compatible version of macOS or OS X on your new hard drive. So, it doesn’t matter if you want a clean slate on a second-hand MacBook or if you replaced the drive in your age-old machine, we’ve got you covered. In this article, we’ve given detailed instructions for each method. Fortunately, there are also several ways to do it, ranging from Internet recovery to installation discs. There are several reasons you might need to install a new copy of macOS or OS X on the hard drive in your Mac or MacBook.

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