Where can I find the source code for the pxeboot image?

["Tim Currie" <tim algernonsystems com>]

Hi!
  I'm having trouble getting kickstart to work and I need to get into the
internals of the pxe boot image (found in /images/pxeboot on CD #1).
Does anyone know where I can find the source for the various things
inside the initrd? Specifially, the 'loader' program?

Thanks,

-Tim

p.s. If you're curious, here's the Reader's Digest version of the problem:
  I have 32 Dell PE2650 servers, internal Broadcom interfaces disabled,
Intel E1000 interfaces installed, E1000 #1 set for PXE boot, BIOS boot
order set to boot from PXE before internal SCS disk. The DHCP server is
set up to provide the PXE clients with everything they need, including
the boot kernel, initrd.img file, and kickstart server info. All are
connected together across a series of Dell 5224 gigabit switches.
  When any of the PE2650's is booted, it sends out the DCHPDISCOVER, the
DHCP server returns a DHCPOFFER, the NIC downloads the PXE client image
and runs it, which in turn downloads the kernel image and the initrd.img
file. The kernel boots and all goes swimmingly until it comes time to
connect to the NFS server defined in the pxelinux.cfg/default file in
order to download the kickstart file. The NFS mount command hangs, the
kernel gets bored and the install drops back to manual mode.
  Here's the bizarre part: if I unplug the nodes to be installed from the
Dell gig switch and plug them into a simple 10/100 hub, the process
works fine: the NFS mount succeeds, the kickstart file is downloaded,
the OS isntalls just fine.
  After careful experimentation, thoughtfull analysis and a few solid
Scientific Wild-Ass Guesses, I've come to the conclusion that the amount
of time it takes for the E1000 to link-up with the Dell gig switch is
somewhat longer than the kernel is willing to wait for the NFS mount
command to succeed. Since the 10/100 auto-negotiation process is simpler
(and therefore takes less time), the mount command cpletes in time and
the kickstart process proceeds.