I'm running Ubuntu 12.04 w/Gnome and have downloaded Mint13 i386 w/Cinnamon and I'm trying to write the iso as a bootable to be used just like a pendrive. I have found no help... probable my lack w/google. Does anyone know how, Unetbootin won't do it.

Are you trying to put a bootable iso on a flash drive?
Are you trying to boot the iso file from the hard drive?
You need to clarify what you are actually trying to do.

The WD 750 gig Passport is a usb harddrive and I want to do this with several systems if possible. I'm hoping to use them like a live CD.

If you want to put the Linux Mint iso file on another disk and boot it as a Live CD, you will need to create a partition on the disk and format it (ext3 or ext4). You can then just copy the iso file to the / (root) of that partition and put an entry in the Ubuntu grub.cfg file for it. I have this set up but on the same partition as Ubuntu with the following entry:

You will need to change the partition number from "(hd0,5)" to whatever is correct for you. You will also need to change "mint12.iso" to whatever the exact iso file name is.

Thanks yancek,
In Nautilus under Devices from the top down I see /media/WD Unlocker, /media/passport, /media/NTFS. When I purchased the device it was formated .ntfs and to leave the Western Digital tools in place I left a small ntfs there and reformatted the new partician as .ext4 where my backups are now found. Since the disk is not bootable I believe I'll need to gpart andchange some things.

I'd put linux partition ahead of the ntfs. Use gparted to move it.

Don't know why you want to boot to an iso. 740 G ought to be left over to 100 different native installs.

Actually, as per my OP, I want to turn the iso into a live file just like the live CDs. If I an figure that out it is exactly where I ve been ointed a along.

To make a USB flash drive or hard drive behave like a live CD you need to extract the contents of the iso into the hard drive and install syslinux/extlinux into the boot sector of the said drive.

Extlinux works with ext2 and syslinux with fat filesystems.

The CD uses a version of syslinux called isolinux, so the same config files should work after renaming them to the appropriate names. You can boot several live CD images from the same USB disk that way, you just need to combine their isolinux.conf files into a single syslinux.cfg.

That I have assumed someone besides myself knew that and asked for a how-to, wouldn t it havebeen really nice if you had done more than to demonstrate that you know why I asked?

What?

Your statement is a little vague.

Also, the way it's written implies some sort of disappointment due to the lack of a "how-to" that I failed to provide.

yes, that is what I needed in the beginning and I still have the image but nt the OS on the external drive.

I have not found a howto, so everything I know is through finding it out by searching and playing around, but I can try to help you step by step as you go. I also can not provide any guarantee that it's going to boot.

First, how is that hard drive formatted?

Since it is several hundred gigabytes large, and fat32 has it's limitations on size, you will need to partition that disk. I seem to remember that windows was only capable of formatting a fat32 volume to 32GiB, which will leave you with a good chunk of useless space.

If you want to use fat32 for Windows compatibility, back up all of the important data on that drive and create two partitions (or more if you like), maybe dedicate 4 or 8 GiB to the first partition if it's only going to be used for live CD images. Partition and format the rest of that drive as you please. You could also pick ext2 if compatibility with windows is not important.

After you format the partition, you need to tell me what system (windows or linux) you will use to install syslinux.

If you use linux, download the syslinux package, mount the target partition somewhere (/mnt/hd for example) and run syslinux in that directory. If you use ext2, before installing extlinux, you need to "dd" the mbr.bin that ships with the syslinux package (to the hard drive itself, not the partition).

Then you loop mount the .iso and "cp -a /mnt/iso/* /mnt/hd/".

After the iso is copied to the hard drive, rename the isolinux.cfg to either syslinux.cfg or extlinux.cfg, depending on which one you decide to use and you should be able to boot from that hard drive.

A little word of caution: Some live CD images probe the live CD media to see if it's writeable, if it is, the boot script mounts it with "rw,remount" and puts persistence files on that media. There are some boot parameters you can use on some of those live CD distros to prevent this behavior, but you are rarely warned about that by the boot process. Why is this bad? because you can't power the machine off by unplugging the power cord without corrupting the file system.