So the computer I am working with doesn't have a hard drive nor a CD drive and I intend to boot it from a "live external hard drive" but when I try to format it using UUI (Universal USB Installer) the drop down list doesn't recognize the hard drive as a flash drive. Is there a way to fix this or another software I could use to format my external hard drive?
The UUI looks for USB flash drives and there is a diference between USB flash drive and USB HDD. To be able to use your USB HDD as a live HDD, open UUI and ensure that the "Now showing all drives(BE CAREFUL)" check box is checked. Then you should be able to view your USB HDD in the drop down. Be very careful while using this option because it will list all the drives and you dont want to end up formatting any other drive
Image source: PendriveLinux.com