Wait, you're trying to install from the USB HDD, like installing from a thumb drive? Or you're trying to install to the USB drive? If the BIOS isn't detecting the drive, well, it just won't work, use a disc. If you're trying to install to the USB drive...why? No room for a small partition on the internal HDD? You could try setting up a virtual machine stored on the USB drive. Am I missing something here? Is it a x64 CPU? Should work fine, right?
Trying to install from the USB HDD to the Internal HDD. I know you can do it from a thumb stick, so I figured you could perhaps do it from a USB HDD?