Check this site if you want to extract the bootloader from original Windows XP CD. *www.helpwithwindows.com/WindowsXP/winxp-sp2-bootcd.html
Second thing, the bootable CD wizard I had mentioned has its own bootloader.You can create images of bootable floppies and put them under the folder images and choose to boot from any of these bootable images by incorporating appropriate commands in the bcdw.ini file in the multiboot project.A template is given in the wizard.The sample from my multiboot rescue CD is given below.
[MenuItems]
C:\ ; Boot from drive C:
\BART\setupldr.bin ; BART Rescue CD
\Images\PQMAGIC.ima ; Partition Magic 8.0
\Images\EBD.ima ; Emergency Boot Disk
owerOff ; Power Off
The last two are the bootable floppy images of Partition Magic 8 (two floppies) and Emergency Boot disk (one floppy)floppy. The message I want to drive is that in case you have bootable floppies simply making the images and putting them in the images folder and incorporating appropriate commands in the ini file you can create a multiboot disk.
n your case I think it is going to be simpler if you do not want to incorporate the BART PE CD. In my case the complexity arose in creating a BART Rescue CD by including the SATA Raid drivers in order to recognise my Raid configured Hard disks in both my systems and the Nvidia Raid drivers required quite a bit of renaming which I had to research and find out.Further the Partition Magic creates a two floppies from which to boot and I had to combine them together and create an image.These two tasks took the hell out of me.
In any case decide first whether you want to go the Magic ISO way or the bootwizard way.Choice is yours. Good luck.