Bootable tool to image hard disk over network

I'm looking for a tool, preferably a minimal Linux build, which can, or fairly simply be modified to, boot as an ISO image and automatically download a disk image over a network and apply it to a blank disk.

In actual fact, I'm fine dealing with the actual scripting to make this happen, but I need at least a base image which will have network access, curl, dd etc, to be of use to me. I'm not looking for any flexibility of choice here, I need it to be totally hands free and dumb, but need to achieve this tasks with as little dev work as I can manage. I think I could possibly just make my own initrd or such, but I've no idea how that works with having network access etc.

[background]This is actually for use with KVM virtual machines, which will eventually be running W2K3, but to deliver the disk image using a wider build framework of cobbler and koan I would rather boot some installation media which will autonomously install a system and reboot when done, allowing a similar higher level flow as installing Redhat with a kickstart script (but without the external resources etc...), so I don't want to pre deliver an image to the host etc, as that's done for a kickstart[/background]

Thanks

Chris

EDIT: So whilst the solutiosn given are valid in their own right, I really needed to NOT have a self contained solution, and needed only a few pieces to integrate into cobbler / koan etc...

What I've currently done is to use a modified kickstart script to initially boot as if to install CentOS but then in the %pre section is just do a wget to download a disk image and smear it across the virtual disk. on reboot, one windows box! Works much better than I thought and also keeps the deployment flow and wrapper scripting totally standardized.