In certain circumstances, Boot Camp Assistant might stop responding, or it might say that Boot Camp installation failed while copying the Windows installation files. Follow these steps to resolve the issue:
If you're in Boot Camp Assistant and it isn't responding, use Option-Command-Escape (Esc) to force the app to quit.
- Install the latest macOS updates, which can include updates to Boot Camp.
- Download the latest edition of Windows 10 from Microsoft's website. Then use Boot Camp Assistant to install it.
If Boot Camp Assistant says that the startup disc cannot be partitioned or restored to a single partition, complete these additional steps:
- Open Disc Utility, which is in the Utilities folder of your Applications folder.
- Select your Mac startup disc (Macintosh HD) in the sidebar.
- In the Disc Utility toolbar, click Partition.
- If Disc Utility asks whether you would like to add a volume to the container or partition the device, click Partition.
- Click OSXRESERVED in the graph that appears, then click the remove button (–) below the graph.
- Click BOOTCAMP in the graph, then click the remove button (–).
OSXRESERVED and BOOTCAMP are empty partitions that Boot Camp Assistant created during the failed installation.
- Click Apply, then click Partition to confirm.
- Open Boot Camp Assistant and try installing Windows again.