Sure. Insert disk 1 and restart the computer, holding the C key from when the startup chime sounds until the Apple logo appears on the screen.
Once the OS finishes booting, choose a language, then choose Utilities -> Disk Utility from the menu. Select the computer's hard drive in the left-hand column, which should be listed as something like "298.0 GB SA1234567890 Media", click the Erase tab, then click Security Options. Select 7-Pass Erase, then click OK. Leave the volume format as-is, but name the drive "Macintosh HD". Click Erase, then leave the computer for a few hours as it does its thing.
Once the erase completes, close Disk Utility and proceed with the install process. Just leave everything as the defaults.
When the computer restarts, hold the option key until the boot menu appears, then hold the power button until the computer shuts off. When the new owner turns the computer on for the first time, they will see the welcome video and be prompted to set up their user account, just like they would with a brand new computer. All of your data is securely erased and unrecoverable.
