If you're going to make a bootable DVD, don't just burn the .ISO file to the DVD. Your burning software should have a "Burn Image" option. That's the one to use to make the DVD bootable.
(I had a friend who just burned the .ISO (not using "Burn Image") to the DVD and couldn't figure out why it would not boot.)
If your computer can boot from a USB, then it's very simple to create a bootable pen drive (should be a least 4GB in size) using the Universal USB Installer program:
http://www.pendrivelinux.com/universal-usb-installer-easy-as-1-2-3/
The beauty of bootable USB is that you can reuse the pen drive for other things -- like testing another Linux distro ;)
I personally use uNetBootin.. works like a charm for me.. some people seem to have problems with it though :p