Wubi External HDD Boot with grub 1.99

A far better way to install Ubuntu on an external hard drive so that it is usable on multiple machines is to install it normally, by booting from an Ubuntu install CD/DVD or USB flash drive, select the external hard drive as the drive to install on, and during the installation, specify that the boot loader (GRUB2) is to be installed to the Master Boot Record of the external hard drive you're installing on, rather than to any other drives in your computer. That way, to boot the system on any computer, just plug it into a USB port and select "external USB drive" (or similar) in the BIOS boot menu. (The BIOS boot menu, like the BIOS setup, can be loaded by pressing a special key, which differs from manufacturer to manufacturer, while starting up the machine. For example, on most Dell machines, it's F12. This is separate from the BIOS Setup, where you can adjust the permanent boot order.)

If you install an Ubuntu system with Wubi on an external hard drive, that hard drive is not rendered bootable. A Wubi system can only be booted on a computer that has Windows installed (or manually, with great effort and needless complexity), and even then, the Windows system has to be modified to add an entry for Ubuntu in the Windows boot menu. Therefore, Wubi is probably a very poor approach for accomplishing your goal.

Finally, please note that:

(1) If you want your portable Ubuntu system to run on as many computers as possible (i.e., almost all PC's and Intel-based Macs), you should install a 32-bit system, as a 32-bit OS will run on a 64-bit processor, but a 64-bit OS will not run on a 32-bit procesor.

(2) Hardware differences besides processor type, varying from one machine to another, might possibly cause your portable system to malfunction in some cases. (But using Wubi would not help with this.)

(3) If you don't need to make any customizations to your system, then you could write an Ubuntu live CD .iso image to the external hard drive. This would deal with the issues described above (2), but would load and run somewhat slower (and most people would want to be able to customize their OS, for example, to install updates and new software and have them remain installed after a reboot). Since an Ubuntu live CD only takes up about 700 MB, after writing it to the hard drive, you could create another partition in the remaining unused space, for storage--files saved to that partition would survive reboots.

"Also if we got it to boot with the usb cable can you also boot with a esata too?"

Yes, if the drive has GRUB2 installed to its MBR and is bootable as an external USB drive, then it will also be bootable as an external SATA drive, provided that the machine on which you're trying to boot has a BIOS that is capable of booting from an external SATA drive.

Do I need to make a partition to install on the external hdd to begin with? or is that all solved when I boot from the live cd and tell it to install on the external hdd.

The installer on the CD will create the necessary partitions automatically (or, alternatively, provide you with the opportunity to customize them manually, which is somewhat technical). Just make sure to tell it correctly which drive to install on (you don't want it to install to the wrong drive).

If you currently have documents or other important data on the drive, you should back it up first, because there is always a small but significant chance of data loss when dynamically resizing partitions. If you have nothing (or nothing of value) on the hard drive and you want to erase any data that's on it, then you needn't make a backup.