I copied bzImage to C:, entered command prompt C: (admin) and renamed bzImage.txt to bzImage. That worked and successfully removed the txt extension and association. Seems like their is still a problem with the file, not sure if it gets corrupted when downloading as txt and renaming it. I copied the plain vanilla looking bzImage to the SD card, re-booted and the Galileo failed at the same point in the GRUB. Error 15 file not found changed to Error 13: Invalid or unsupported executable format. Sounds to me like the OS is still having problems reading the bzImage from the SD.
I am getting the same exact error as bamacken on Feb 28th reported above.
I will have to resolve the bzImage file downloading problem. File should not download as a TXT have to be renamed to non-txt, this must be part of the problem.