To wipe your old 2009 iMac, follow these steps:
1. Start by shutting down your iMac completely.
2. Once it is turned off, press and hold the Command (⌘) and R keys on your keyboard.
3. Keep holding these keys until you hear the Mac tone indicating a reboot. This will boot your iMac into macOS Recovery mode.
4. When the macOS Utilities screen appears, click on “Disk Utility” and then click “Continue.”
5. In the Disk Utility window, you will see a list of drives on the left-hand side. Select your iMac’s system drive, usually named “Macintosh HD” or something similar.
6. Click on the “Erase” button at the top of the Disk Utility window.
7. A pop-up window will appear where you can choose the format for your iMac’s hard drive. If you want to completely wipe all data on the drive, choose “Mac OS Extended (Journaled).” You can also give it a new name if you prefer.
8. After selecting the format, click on the “Erase” button. Please note that this will permanently erase all data on your iMac’s hard drive, so make sure you have backed up any important files beforehand.
9. Disk Utility will now erase the drive and reformat it with the chosen format. This process may take a few minutes.
10. Once the erasing process is complete, you can close the Disk Utility window.
11. From the macOS Utilities screen, you can now choose to reinstall macOS or quit the macOS Utilities to shut down your iMac.
By following these steps, you will be able to wipe your old 2009 iMac and start fresh. Remember to back up any important data before proceeding, as erasing the drive will permanently delete all data on it.