By default, the name would be Macintosh Hard Drive. Make sure that the drive format is set to 'OS X Extended Journaled' and type in a name for your hard drive. OS X will then ask you to verify that you are going to erase your hard drive.

The 'Erase' button is the much faster option. If you just want to erase your hard drive and install Snow Leopard, click erase. If you want to erase your hard drive securely with no chance of data recovery, click security options and select Zero out disks. You will see three options: erase free space, security options, and erase. Next, click the 'Erase' tab located in the center of the disk utility window. You will see your hard drive listed along the left side of the disk utility window. Disk utility should now be opened and visible on your screen. Click 'Utilities' and select 'Disk Utility'. You should see a drop down list for 'Utilities'.

Now, move your mouse cursor towards the top of the screen and the OS X menu bar will appear. Click continue to proceed to the next screen. The first screen you get will say 'Welcome to OS X Snow Leopard'. You may have to wait a couple of minutes for OS X to load the disc. As soon as you see the Apple logo with the spinning wheel, you can release the 'c' button. This will force the Mac to boot from the disc. As soon as you hear the chime of the computer restarting, immediately hold down the 'c' button on your keyboard. To start the clean install, insert your OS X Snow Leopard disc into your Mac and restart the computer.

Snow leopard update