Air Disk Help

Hi i hoping some one can help! i have a macbook running the latest version of leopard and i also have a external hardrive which is connected the the usb plug on my airport extreme which works as an air disk. My brother has an older G4 imac which runs Mac OS 10.3.9. Is there any way that i can set up his mac to be able to see/use the air disk? at the moment it appears in my finder window straight away but not in his?

P.S we are both in the same house on the same network.

Thanking you in advance!

Aaron