If you did not get an OS X install-restore DVD with the computer you may need
to buy one from somewhere, and you may be lucky to get a retail OS X 10.5.x
version. The original grey-label install set of software and OS X it shipped with
likely would be an older system than Leopard 10.5. Last versions of G4 Mac, &
G5, shipped with a Tiger 10.4 system; so did early Intel-based Mac. Grey discs
which accompanied other computer build models generally do not interchange.
The last OS X version a PowerPC architecture can use, if supported, is 10.5.8.
A PPC processor at 867MHz & faster should be able to run OS X 10.5 Leopard.
{With the correct disc installer, you can use it to change a password and other
things including re-install, and perform disk utility functions, etc.}
There is a chance you may be able to get a white-label Replacement 10.4 DVD
or Replacement 10.5 DVD from AppleCare or the online Apple Store (800myapple)
from a Mac OS X system specialist; these have been available yet hard to get
as not all persons involved with them seem to know if they still exist until someone
is asking. These aren't retail stock, are special discs for computers who could use
a system later than original old discs; these are complete install discs not for one
specific series of Mac. Generally they'd work in supported PowerPC G4/G5; but
do not replace specialized original install DVD, such as an early Intel mac requires.
You'd need to have a serial number of the computer, and a method of payment
when seeking some replacement system media from Applecare or Apple sales
and these discs are not available in a retail store. The original Retail discs are
labeled differently and shipped in a retail box with a big X on the front. Other
sources for retail 10.4 Tiger or 10.5 Leopard may be online via amazon sellers
or computer resellers who handle repaired Macs. Avoid mystery grey label ones
that were intended to be sold and kept with their original computer kits.
Good luck! 😐
