Click on the 'First Aid' tab at the top of the Disk Utility interface. Open the 'Utilities' menu and choose 'Disk Utility' to launch the application. Click on the right-arrow button at the bottom of the dialog box to continue. Select your language from the list that appears when your system restarts. Continue to hold down the 'C' key until you see the startup progress indicator, shaped like a spinning gear. This key command tells your system to start from the bootable installer you inserted in your optical drive. Press and hold the 'C' key the moment you hear your system's startup chime or just as your screen blacks out at the beginning of the restart process. Open the Apple menu and choose 'Restart.' When the dialog box that asks if you want to restart your computer appears, click on the 'Restart' button or wait one minute until your system begins to restart on its own. If your system uses a slot-loading internal optical drive, press the DVD into the empty drive slot.

Press 'F12' to open your Mac's optical drive and insert your Leopard installer DVD.

Mac os x utilities screen