Yes, true. The last two commands are the critical part. Probably should ensure there's enough space on the destination(s) before uncommenting the last two lines. This script is non-destructive otherwise. Either way you will have a backup in $BUIMG (assuming you follow the directions and use a 2nd form of media for $MYDATA with enough space there).

I now boot my HD like a USB drive using grub4dos so I can still boot WinXP in a pinch (even tho I have a Win7 and XP VirtualBox) so there''s plenty of space. Note the following wont work for grub2....
Code:
 Installing a USB compatible install non-invasively(sp?) to the HD
- Do all this from usb booted knoppix
- get grub4dos and extract the zip somewhere, then cd to that extraction area
  unzip grub4dos-0.*
  cd grub4dos-0.*
- mkdir /mnt-system/boot/grub
- ensure the /mnt-system/boot/grub dir has grub's menu.lst:
  cp menu.lst /mnt-system/boot/grub
- create the MBR if and ONLY if it doesnt exist:
  sudo bootlace.com  /dev/sda # trashes existing MBR careful!
- copy grub.exe to the /mnt-system/boot/grub area for DOS/98/XP/NT/W7/VISTA
  cp grub.exe /mnt-system/boot/grub
- cp the grldr to the root of the hard drive:
  cp grldr /mnt/sda1
- add the following lines from the boot/syslinux/syslinux.cfg:
  Note: the kernel line contains everything from the syslinux.cfg append statement except the initrd=stuff (even tho it can be left in place)
# this is a long cmd so be careful!
# this will /insert lines before the first title in menu.lst - and the kernel line will ignore the initrd=...
   sed -p '/title/i\ 
title knoppix # any name to describe this boot
root (hd0,0)  # /dev/sda1 - note the kernel line is from a knoppix 6.23 cfg
kernel /boot/syslinux/linux ramdisk_size=100000 lang=en vt.default_utf8=0 apm=power-off vga=0x311 initrd=minirt.gz nomce quiet loglevel=0 tz=localtime
initrd /boot/syslinux/minirt.gz 
/' /mnt-sytem/boot/grub/menu.lst

- now the boot/ and KNOPPIX/ dirs need to be copied to the /mnt/sda1 destination
- copy /mnt-system/{KNOPPIX,boot} to the hd partition:
  cd /mnt-system; for dir in KNOPPIX boot; do cp -av $dir /mnt/sda1; done