Connect a blank USB flash drive or insert a blank writable DVD. You can install Windows 10 by creating a bootable USB flash drive or DVD that contains the Windows 10 installation files. You'll need a USB flash drive that's at least 8GB, or any blank DVD to get started. If you already have Windows 10 installed on the PC and just want to reinstall it, it'll be easiest to reinstall it from within Windows 10 instead of creating installation media. If you want to upgrade from Windows 7 or Windows 8.1, you won't need to create an installation disc or drive. However, you will need to follow most of this method to start the upgrade.

Make sure you have a product key. If you bought Windows 10 through Microsoft using your Microsoft account, your product key is already linked to your account. If you bought Windows 10 from another retailer, you'll have a 25-character product key that you'll need to have handy to activate Windows. If you don't have a product key or you're installing Windows 10 on a new hard drive, make sure you've linked your Windows 10 digital license to your Microsoft account before you start the installation. Head to Settings > Update & Security > Activation from the current installation—if the activation status says Windows is activated with a digital license, click Add an account and follow the on-screen instructions to link your Microsoft account. If you're upgrading from an earlier version and your PC qualifies for a free upgrade, you won't need a product key.