it is a HOWTO of booting ONLY the MRI pe from usb .
from following link download grubinst-gui
http://nufans.net/grub4dos/grubutil/grubutil-1.1-bin-w32-16.zip
, from disk , select ur attached usb drive (make sure ur drive is empty and formatted as fat32) ,
click install , a dos windows should open ,saying successfully installed MBR .
now download grub4dos's latest package from here, (grub4dos 0.4.4 )
http://sourceforge.net/project/downloading.php?group_id=104188&filename=...
and copy grldr and menu.lst from the package to the root of ur drive .
open , menu.lst and delete everything from there , now copy paste the following
# This is a sample menu.lst file. You should make some changes to it.
# The old install method of booting via the stage-files has been removed.
# Please install GRLDR boot strap code to MBR with the bootlace.com
# utility under DOS/Win9x or Linux.
color blue/green yellow/red white/magenta white/magenta
timeout 30
default /default
title MRI BOOT
fallback 1
find --set-root /BOOTMGR
chainloader /BOOTMGR
savedefault --wait=2
title MRI BOOT (if first fails)
fallback 2
find --set-root --ignore-floppies /BOOTMGR
chainloader /BOOTMGR
savedefault --wait=2
now , mount ur mri iso image using any tool or extract it , and copy all the cd to ur usb AS IT IS . ur usb SHOULD at least boot fine . although it never loads the MRI main file at the end for some reason . just sharing it here because many members asked it in pm . and sadly i misplaced that gho image which i sent to a member here a while ago .
use recently cracked MRI pe . the above method was tested with MRI 0.5.1 . but it should work with latest one too .
plz remember booting from usb is highly defendant on ur bios . so check the options closely in ur bios . there is no 100% way of booting usb from every system .