When you put the Ubuntu 12.04 Live CD/Install CD in and start the computer, instead of saying "Press any key to boot from disk.........." and going to hard drive boot upon no key press, which is what happens with other disks, it automatically starts the disc. How does this happen? What's going on?
Check your boot device priority first. Is it set to CD-ROM? If not, change it.
This message is not related to BIOS, but it's what Windows boot disk use.
What I mean is that BIOS hands the control to any bootable CD the same way it does to a Hard Disk. Windows CDs then, by themselves, show this message, and if you hit any key boot from the hard disk.
If you build a custom Windows CD (with nlite) you can disable this prompt.
In short: Ubuntu does nothing to the BIOS, this message is a Windows thing.