Serving ISOs via Netboot?

I have an Mac OS X 10.6 server that is currently hosting some netboot images for DeployStudio. Everything there works very well. However, We have some Macs that are running Windows, for which we are not using DeployStudio. We have a WinPE and Ghost environment for all of our Windows machines. In order to image these Macs to Windows, we have a bootable CD that will take them to the WinPE environment.

I'd like to take the CD out of the picture and just have the Macs boot to the ISO that is used to make that CD. However, I cannot figure out how to do it. I made copies of my working DeployStudio NBIs and pointed them to the ISO by changing the NBImageInfo.plist. When attempting to boot these Macs to the new NBI, I just get a circle with a line through it. I also tried making a DMG with Disk Utility, and a SpareImage with Carbon Copy Cloner, and those do not work either.

I know I must be missing something somewhere if they can boot to the WinPE environment with the CD, but not via netboot. Can anyone help point me in the right direction? Thanks in advance for your help.