When you boot from the Installer DVD and after you select your language, you need to choose Disk Utility from the Utilities menu bar. When it launches, you need to initialize the drive by clicking on it (and not any partitions that might be below and indented), then click on the Partition tab, choose 1 volume from the pull-down (or more, if you like), then click on the Options button and choose GUID if you have an Intel Mac, or Apple Partition Table if you have a PowerPC Mac. After initialization, the drive should show up in the Installer.