Booting a live distro from HDD

How can I make a live distro (eg Knoppix) to boot from the HDD. Is it easier if there's alredy another distro installed?(so there's an existing bootloader to assist)

Try a cheat:
install a distro to get the bootloader.
Then erase any thing except the /boot directory to preserve the bootloader

http://www.knoppix.net/wiki/Win_Partition
This is called a poor man's install. You can install to an existing Windows partition (including ntfs) without messing with the MBR. The disadvantages are that it acts like it's running from the CD, so you can't install anything. This will work with Windows XP, 2000, NT, or with a few modifications 98, and supposedly 95 (I haven't tested it.)
You can also install any livecd that has an option to boot from iso. Just get the kernel and initrd from the cd.

TruongAn said:

Try a cheat: install a distro to get the bootloader. Then erase any thing except the /boot directory to preserve the bootloader

...and then? Which files from the live distro CD I copy to the partition? And how do I delete the rest of the files from the terminal without making the PC to crash?!

http://www.knoppix.net/forum/viewtopic.php?t=11796
Here is a VERY long thread that eventually results in a usable method for running an .iso image from a hd. I have used this method to run Knoppix 3.7 from an iso image stored on an ntfs partition.