Ubuntu Live Cd On Windows 7 Issue?

I downloaded ubuntu-12.04.2-desktop-i386 iso.Then i burn it to a DVD.But i can't run it as a live cd on Windows 7.I changed the bootable device oreder of BIOS also.Why is that?
Thanks

How did you burn it? Did you burn the ISO to the disc as a file, or as the complete image? It must be written as a complete image, and then you need to verify the disc checksum (md5sum is most common) to the iso checksum to be sure it was written successfully.

When you burned it onto the CD, did you burn it as a bootable image??