オリジナル投稿者： Dan ,
You’ll need to boot up under an external bootable drive to fix your drive. I would recommend you make a full backup using TimeMachine so you can properly fix your drive. Sadly it will need to be reformatted and a fresh OS install (MacOS & Windows) to fix this as the boot sectors are damaged. Often times I see this with BootCamp installations when a Windows virus attacks the drives boot sectors. I would strongly recommend you get a good antivirus app that runs under MacOS & Windows as well. Here’s how to create the needed boot drive: [https://www.macworld.com/article/3092900/macs/how-to-create-a-bootable-macos-sierra-installer-drive.html|How to create a bootable macOS Sierra installer drive] Go to your Apps Store app and open the Purchase tab to locate your OS to re-down load it.