I want to multi boot Linux (Fedora 19) with my two machines which use Windows 7 and 8. The Windows7 is a desktop, and the laptop is a Windows 8 machine.
I used my desktop to install Fedora 19 on the external drive. I can boot Fedora from the desktop but not the other machine. To be clear the portable machine can boot from USB hard disk, I've checked the BIOS.
I found that an easy way to boot Linux or any other OS is using an OS independent boot manager. I downloaded Boot-US and tried it out. However when I load it up and it shows the disks it says my desktops primary internal HDD is bootable. The other one, the external disk does not. I checked the help section for the program (specifically Linux Tip (2)) and it required that I edit Lilo.
I know Fedora 19 uses Grub 2 in place of Lilo and I wouldn't know how to safely edit either boot loader anyway.
Could somebody help me install this OS to my external Hard Disk and still be able to boot from that when on my desktop OR laptop?
 I have a UEFI BIOS on both the desktop and the laptop. I installed Fedora 19 to the external hard disk by use of a LiveDVD.
To the contrary of what the comment below says Boot-US should be able to boot from almost anything. It recommends that you try your first boot from a diskette (something nobody uses anymore) or a CD. It can also be installed to the MBR on the Hard Disk but that could make the system impossible to boot if done wrong if I am correct in remembering.