HI,
The simple answer is yes you can, All you will need to do Is configure the airport to connect to the D-Link as a wireless client then it should show up in the bottomleft of iTunes as an Airtunes device so you can select it and stream from your G4 iTunes library.
Let us know if you need instructions or more info.
ThanksEric
Ok,
do you have any machine that is wireless in your home?
Thanks
In that case we are going to have to direct link the airport to your computer via ethernet cable, Once you have them connected can you then run the airport setup ad see if you can now see the express to configure it to join your existing wireless network then unplug the ethernet from the express ad plug back into the Router once the airport is configured
Let me know if the hardwire does not work to configure it.
IEEE Network Engineer, Microsoft
approx 20 years of experience from software to hardware design
Take your time and let me know if you have any issues
More than welcome.
Also bear in mind that now the airport is wireless you can also use it as a wireless bridge to provide a network connection to a device, So if you wanted to move your mac you could plug in like you were when you set it up and it will allow your mac to connect wirelessly.
Thanks for using JustAnswer.com and please let us know if we can be of any help in the future.