I just received a Mac iBook G4 (Mac OS X 10.5.8) from a seller on eBay and want to know how I can ensure that it is virus free. I am a Windows programmer and IT person, so when I receive a new Windows computer that was used I do a complete wipe of the computer. This Mac never came with an installation CD/DVD and it seems hard to find them online as you seem to have to buy the OS new.
You should re-install the OS completely.
You need to boot the iBook from the CD, to do so, put the install cd inside, power off the computer, turn it on and immediately press the C key. That should bring a boot menu, allowing you to choose the install CD.
From there you should just follow the instructions on screen.