To delete an old startup disk on a Mac, you can follow these steps:
1. First, make sure you have a backup of any important data on the startup disk. This is crucial to avoid losing any important files or documents.
2. Restart your Mac and hold down the Command and R keys simultaneously during startup. This will boot your Mac into Recovery Mode.
3. In Recovery Mode, you will see the macOS Utilities window. Select “Disk Utility” and click “Continue.”
4. In Disk Utility, you will see a list of all the drives connected to your Mac. Choose your old startup disk from the left panel. It is usually named “Macintosh HD” or something similar.
5. Click on the “Erase” button at the top of the Disk Utility window. This will bring up the erase options for the selected disk.
6. You will be prompted to choose a name for the newly formatted disk. You can use any name you prefer, even the same “Macintosh HD” name as before.
7. Select the appropriate file system format for your needs. If you plan to use the disk with a Mac, choose “Mac OS Extended (Journaled).” If you intend to use it with both Mac and Windows computers, choose “ExFAT.”
8. Double-check that you have selected the correct disk and chosen the desired options. Once you are certain, click on the “Erase” button to start the erasing process.
9. Disk Utility will warn you that erasing the disk will delete all data on it. Confirm your decision by clicking on “Erase” again.
10. The erasing process may take some time, depending on the size of the disk and the speed of your Mac. Once it is complete, you will see a confirmation message.
11. Close Disk Utility and choose “Restart” from the Apple menu to exit Recovery Mode and boot your Mac normally.
It’s important to note that erasing a startup disk will remove all data from it, including the operating system and any installed applications. Therefore, make sure you have a backup of any important files before proceeding.
Additionally, if you are erasing the disk to reinstall macOS or to use it as a new startup disk, you will need to reinstall the operating system using the macOS Utilities in Recovery Mode.
Remember to exercise caution when erasing a disk, as the process is irreversible and can result in data loss if not done properly. If you have any doubts or concerns, it’s always a good idea to seek assistance from a professional or consult Apple’s support resources.