How to make a multiboot CD/DVD (Merge Bootable ISOs)

with 4 basic options
1. boot from primary harddisk
2. xp sp3
3. bart pe
4. reboot

use g:\cd
as my root folder& my file structure is for boot files
g:\cd\boot\isolinux
g:\cd\boot\bartpe
g:\cd\boot\xpsp3 for respective cd content
g:\cd\bartpeg:\cd\xpsp3

use isolinux.cfg as
------------------------------------------------
DEFAULT /boot/isolinux/vesamenu.c32
PROMPT 0
TIMEOUT 300
TOTALTIMEOUT 450
####
MENU BACKGROUND /boot/isolinux/splash.png
MENU TITLE XPSP3 + BARTPE
####
#### The 1st byte of the fgnd color is brightness.
#### blue
MENU COLOR title 1;36;44 #ff0000ff #00000000 std
#### blue
MENU COLOR unsel 37;44 #ff0000ff #00000000 std
#### white
MENU COLOR sel 7;37;40 #c0ffffff #ff000000 std
#### red
MENU COLOR hotkey 1;37;44 #ffff0000 #00000000 std
#### green
MENU COLOR hotsel 1;7;37;40 #ff00ff00 #ff000000 all
####
LABEL bootc
MENU LABEL ^boot from C:
MENU DEFAULTKERNEL /boot/isolinux/chain.c32
APPEND hd0
LABEL bartpe
MENU LABEL ^BartPE/WinPE
KERNEL /boot/bartpe/bSETUPLDR.BIN
LABEL xpsp3
MENU LABEL ^Unattended XP SP# Pro Installation
KERNEL /boot/xpsp3/xSETUPLDR.BIN
--------------------------------------------------------

& edited SETUPLDR.BIN using hexedit & replace i386 to bartpe/i386 in case of bartpe
& replace i386 to xpsp3/i386 in case of xpsp3
& rename as bSETUPLDR.BIN &xSETUPLDR.BIN& place in
g:\cd\boot\bartpeg:\cd\boot\xpsp3 resp
now to make cd use mkisofs.exe of pebuilder
& created bat to automate process
----------------------
@ECHO OFF
ECHO Starting @ (%TIME%) ....
SET _VNBR_=01
SET _ROOT_=G:\cd
SET CDTITLE="cd-%_VNBR_%"
SET CDFILENAME="%_ROOT_%%CDTITLE%.ISO"
C:\pebuilder3110a\mkisofs.exe -N -V %CDTITLE% -b isolinux.bin -d -iso-level 4 -no-emul-boot -boot-load-size 4 -boot-info-table -o "G:\ISO.iso" "G:\cd\boot\isolinux"
--------------------------------

but all this creat bootable iso of 1.44mb
then use magiciso to add other files from the cd folder & save it
the image is bootable