Dell NIC drivers not working with WinXP boot image, but does with Win7 boot image

Deployment Server: Microsoft Windows Server 2008 Standard SP1 x86

Background:
I have an image of Windows XP Pro SP3 32-bit for a specific group of user PC's, the image was built on a VMware virtual machine (on Intel CPU's). Of the 130 PC's there are Dell Dimension 2350's, 3000's, 4600's, and Optiplex 740's. The 740 is a AMD processor so I had to disable the IntelPPM.sys file from starting at boot before sysprep. That, and using the general ACPI driver allows my XP image to load on both my AMD and Intel CPU workstations, and it has been working great for years.

Situation:
Now we just bought a bunch of Optiplex 790's and I figured the image would work with these as well, as long as I added the drivers into the image. Unfortunately I can't even get the image on my 790's because I can't seem to get a working NIC driver for my boot image.

I'm not sure how the boot image was built because I didn't build it, but it had the description "universal XP install boot image" so it may have been from the Windows XP disc image, if it had a WDS/RIM boot image. Regardless it has worked on all my Dell machines up until now.

The Problem:
I've added the Dell provided WinPE 2.0 and 3.0 NIC divers (Dell driver deployment site) to my "XP" boot image but when I PXE boot into the image on an Optiplex 790, it gets the error "WdsClient: An error occurred while starting networking: a matching network card driver was not found in this image...".

So I figured I would try my Windows 7 boot image instead, I've already added 790 drivers to it and it works fine for Windows 7 user PC's. The image came frmo the Windows 7 boot.wim that came on the disc. Now the boot image boots just fine on my 790's, but my XP image doesn't show up, yet it shows up on my Dimension 2350's, 3000's, 4600's, and my Optiplex 740's.

Possible Causes:
Now one of the issues I encountered which I believe could be the cause, is when trying to add drivers into my XP boot image, the AIK for Windows 7 wouldn't mount my XP boot image, it would get to 72% and say it couldn't mount because it was in use by a process. It wasn't though, Windows Explorer was closed and nothing was accessing the boot image. I even tried turning off my McAfee A/V scanner, no help. So I went to another machine that I still have the Windows Vista AIK installed which uses the "imagex" command as opposed to "DISM". With Vista AIK, I was able to mount the boot image and add drivers to it just fine. Unfortunately because you can only add driver files one folder at a time and it doesn't have the recursive option that Win7 AIK has, I only did the X86 drivers. I tried both sets of x86 drivers from the WinPE 2.0 and WinPE 3.0 Dell CAB files. Is that my problem? Do I need to do the x64 ones?

Or is there some CPU platform compatibility thing I’m not aware of here between my old PC’s and the new 790? The 790 has an Intel Core i3… but I thought this was just like any other x86/x64 Intel platform that is the same as my Dimension 2350’s, 3000’s, and 4600’s. I also have some Optiplex 755’s and the XP image shows up just fine on that too, just not the 790’s with my Win7 boot image.