Well you just discovered the answer to the problem. You didn't follow instructions to use ImgBurn to burn the Ubuntu file. You took it upon yourself to use another software even though the instructions clearly state to use ImgBurn. You then ask why it's not bootable.
As stated, an iso image file like Ubuntu is NOT the same as burning other data. It must be burned using an iso burning software. Your computer can be set to boot from a cd seven ways to Sunday. If the iso image (Ubuntu) was not burned to a disc using the proper burning software it will not boot from the cd.
The bios boot options on your computer are fine. Forget about the bios. It's a non-issue here. The issue is how Ubuntu was burned to a disc.
There is no need to feel overwhelmed. None of this is rocket science. It only requires you follow directions to the letter and not to stray off on your own adventure. Follow each and every instruction. If you have a question STOP and ask.
Burn the file again using ImgBurn. You can uninstall it when you are done.
Edit: As noted by Davee, if you feel you cannot resolve this issue alone then by all means take the computer to a professional. I would imagine, however, to recover your data and re-install Windows would be quite expensive. If you choose that route make sure they give you a disc and the product key.
