Q: I have a G4 laptop.  Can I put a new hard drive in it?

Yes, although the effort may be called 'Difficult' due to the other items

in the way before the actual task is completed. Not just wires or cables,

the screws are of differing length and so need to be ordered so you can

keep track of their placement for best reassembly.

Replacement ATA/IDE rotational hard drives are harder to get now, and

another better alternative is a product available (example) from OWC

that is a Solid State Drive. Faster, system performance improves greatly

& uses less power. A 60GB example is here for ATA; they do have others:

https://eshop.macsales.com/item/OWC/SSDMLP060/

Among examples shown on the site page where above also is presented

is a rotational hard drive of 60GB, much less costly; does not improve

performance like an SSD does, especially if you use Leopard 10.5.8.

https://eshop.macsales.com/Search/?q=ibook%20g4&filter.catidpath=4081

Instructions on hard drive replacement with additional details in user comment

section, can be found at the iFixit repair guide page for iBook G4. see yours:

https://www.ifixit.com/Device/iBook_G4

Good luck in this matter!

You are welcome. If you have additional question or issues, you

could revisit this discussion thread; or if unrelated to topic, start

another for other concerns. When noted by other helpful persons

here you may see more ideas. Since it is still a weekend in N.A.

the viewing of these ASC areas may be less than other times.

{While I have an iBook G4 12-inch mid-2005 1.33GHz with 40GB HD

& 1.5GB RAM - I've found OS X 10.5.8 way slower than Tiger 10.4.11.

The hard disk drive is original, the computer is close to as-new; and

was bought from Apple 'special deals' online refurbished page in '05.}

Good luck in your adventure.