Click Erase and wait till finished.Įxit Disk Utility and once back on OS X Utilities menu, just select Install OS X and your on your way to a clean install of El Capitan. The name option is up to you, leave Scheme as is. Once the popup appears, select Mac OS Extended (Journaled) for the format option. If not, turn off iMac and hold Option (Alt) ⌥ key immediately after turning on the iMac.Īs to how you format your drive, in Disk Utility select your internal drive (left hand side) and choose erase. Since there is no OS, it should just boot the USB stick.

Ignore the missing partition table popup and hit continue.Īfter Etcher does it's thing, just pop the USB stick into the iMac and turn it on. If you are booting to OSX utilities immediately, your mac either cannot detect your HD or it cannot read the OSX installed on this.

Use Etcher to flash the InstallMacOSX.dmg image to a USB stick. My recommendation, obviously you don't have to. I'll go a long way in just normal day to day usage. If it doesn't already, add 8GB of ram and maybe a SSD. Insert it into the machine, hold down the Option key while it reboots. OS X El Capitan is the last OS your iMac will support. Use the Mac OSX 10.5 (Leopard) installation disk.

Mac os x utilities screen