Booting from ISO image in harddisk

It is always done with root privileges.  

What can be done is u create one file named say ubuntu-live in the directory /etc/grub.d/. And in that file u put the contensts given below starting from echo.

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echo "Adding $(egrep menu[e]ntry $0 | cut -d'"' -f2)" >&2
cat << EOF
menuentry "Ubuntu 10.04 -LTS Live CD" {
loopback loop (hd0,3)/ubuntu-10.04-desktop-i386.iso
linux (loop)/casper/vmlinuz boot=casper iso-scan/filename=/ubuntu-10.04-desktop-i386.iso file=(loop)/preseed/ubuntu.seed quiet splash bootkbd=sg --
initrd (loop)/casper/initrd.lz
}

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Make the file ubuntu-live executable by putting command : chmod +x ubuntu-live

Now update the grub image by  putting command in terminal : update-grub 

Reboot ur machine and Now u can have new grub image ofUbuntu 10.04 -LTS Live CD in the start up promt when grub starts.
Select it.

**attention: it is recommended to put the iso image in another drive. Because when we try to install in the same drive what ubuntu-live-cd will do is format it. So iso image will no longer stay there. It might happen the process break.

Let us Say we put iso image  in hard disk first , i have put it into partitions 3 of first hard disk. so it is written as (hd0,3). and pathname in that partitions. follows.