Updated August 29, 2017
How to Factory Reset an iMac Via the Recovery Partition
Restart the iMac and hold the “Command-R” keys while the computer reboots. Select and connect to a Wi-Fi network from the list if the iMac prompts you to do so. Choose the “Disk Utility” option from the list and click “Continue.” Select the hard drive on which Mac OS X is installed from the tree list on the left side of the window. Open the “Erase” tab. Select “Mac OS Extended (Journaled)” from the “Format:” drop menu and enter a name for the hard drive in the “Name:” text entry field. Click “Erase…” to clear all of the hard drive’s contents. Choose the “Quit Disk Utility” option to exit the disk formatting tool. Select “Reinstall OS X” from the menu, click the “Continue” button and follow the on-screen instructions to complete the OS installation process on your clean hard drive.
How to Factory Reset an iMac Via Bootable USB Recovery Drive
Download the version of Mac OS X the iMac is running from the App Store. Open the “Applications” directory in Finder. Control-click on the “Install Mac OS X” icon and choose the “Show Package Contents” icon. Expand the “Show Package Contents” folder. Copy and paste the “InstallESD.dmg” file to an easily accessible location on the iMac hard drive. Open the “Disk Utility” within the Utilities folder under Applications and connect the USB flash drive to one of the ports located on the back side of the iMac. Choose the flash drive from the left-side tree display and then click the “Burn” icon. Select the “Image…” button, then locate and choose the “InstallESD.dmg” file. Click “Restore” to create the restoration drive. Restart the iMac after the restore drive is completed and hold the “Command-R” keys until the boot selector appears. Choose the flash drive from the boot selector, open the “Disk Utility” and select the iMac’s hard drive. Select the “Erase Tab,” set the “Format:” value to “Mac OS Extended (Journaled)” and then click the “Erase” button. Quit the “Disk Utility” tool when the hard drive format is complete. Choose the “install Mac OS X” option from the menu and follow the on-screen instructions to complete the factory reset. These instructions are based on iMacs running OS X Lion and may vary with other versions of the Mac OS X operating system. Warnings Writer Bio
