I used the NCH burn software to burn the .iso image to a DVD-R; however, when I go to see if there is an .iso file there, it doesn't appear, so I can't select it in the process of installing Ubuntu 12.04 to this flash drive. Any ideas?
Properly burning a .iso file to a disc doesn't place a .iso file on the disc. These files are bit-for-bit copies of the contents of a disc, including the filesystem structure. So what you will see is the files contained in the .iso image, rather than the .iso itself. This is similar to extracting a .zip file (or another archive) to a folder.
To create the Live USB drive, use the .iso file you burned to the CD. If you downloaded this file in Windows and are currently working from the Ubuntu Live CD, then you will need to find your Windows partition in the file browser (it should show up on the left side of the file browser window), and in that drive, navigate to