How to erase the HD of a PowerBook G4 15" running on Mac OS X 10.5.8.

While the Mac is starting up with the install-restore DVD disc in the optical drive slot

you have to hold the C key down, until the computer runs from the startup portion

of the installer.

Erase and Install Method for OS X 10.5 Leopard - Lifewire

Installing OS X 10.5 Leopard using the Erase and Install method gives you the ...

to boot from the Leopard Install DVD. There are multiple ways to start this ...

https://www.lifewire.com/installing-os-x-10-5-leopard-erase-m

Otherwise you won't get past the main feature, the most basic one is to install. Other

'system tools' are available from the menu bar (a finder-like appearance) within installer

once it starts and the internal hard drive can then be accessed by Disk Utility on DVD.

If the hardware is otherwise OK, better to restore useful system over erased HD content.

And re-purpose the vintage machine. I've two older PPC G4 Macs and use TenFourFox

browser for adequate online purposes. ~ There's also the last version iTunes in Apple

software archive for either Tiger 10.4.11 or Leopard 10.5.8.