I think I am going out to buy a network card and I heard that the realtek 8139 series works great natively for leopard. I just want to make sure does this account for the 8139D also, because I have not seen a lot of people use it.

This model is compatible with leopard. I instaled version 10.5.2 and all goes good. Its find netvok card him self and ads.

I had success with the card. I got a Dynex card from Best Buy with this same chipset. All I did was put it in the computer and as soon as leopard booted a message saying that a new network device was detected. That was a couple days ago and my system has been working fine even while streaming to the xbox 360 and my roommates watching vids over smb. I'm glad too cause I was using a wireless usb card and about every 4 hours or so it would cause a kernel panick.