Burn bootable iso image to USB stick using dd: Won't boot (despite USB first in boot sequence)

I have installed Ubuntu on a Lenovo Thinkpad R500 2732, and I must update the BIOS.

On the Lenovo website, I am offered this:

BIOS Update Bootable CD for Windows 7 (32-bit, 64-bit), Vista (32-bit, 64-bit), XP - ThinkPad R500

I guess a bootable CD that would do a BIOS update is indeed what I need. (still wondering why it says "Windows" though... if it is bootable should not it be OS-agnostic?)

Not wanting to waste a CD, I copied the image to my USB stick:

sudo dd if=/home/nico/7yuj40uc.iso of=/dev/sdb1 bs=1M

And rebooted, after making sure USB is first in the boot sequence.

PROBLEM: It does not boot. Did I forget one step?

Details about the iso image (readme):

ls -lh 7yuj40uc.iso
25M
file 7yuj40uc.iso
/home/nico/7yuj40uc.iso: # ISO 9660 CD-ROM filesystem data '7YUJ40US                       ' (bootable)

(Scroll to the right: it says "bootable")

• UNetbootin does not work because it is not a Linux image.
• Some people on the Internet advise to copy the content of the ISO and do other steps. This ISO has zero ISO content so it would not work. If I mount the ISO, I can see it contains zero files.

https://wiki.archlinux.org/index.php/ThinkPad_Edge has the process:

1. Grab and unpack https://gna.org/projects/grub4dos/ (the wiki has an old link)
2. In the grub4dos directory, sudo ./bootlace.com /dev/sdb
3. cp grldr /media/USBSTICK
4. cp menu.lst /media/USBSTICK
5. cp /path/to/7yuj40uc.iso /media/USBSTICK

Finally you have to add the following code to the menu.lst on your pendrive to make the USB-Stick boot the PC DOS program made by lenovo:

title Thinkpad-BIOS-UPDATE
find --set-root /7yuj40uc.iso
map /7yuj40uc.iso (0xff) || map --mem /7yuj40uc.iso (0xff)
map --hook
chainloader (0xff)
boot

And that's about it.