|First, it's a cd you're trying to boot from and not a DVD, right?|
Make sure the cd is bootable. Try it in another machine if necessary.
In cmos/bios setup, the cdrom is set as the first boot device.
In some cases you need to separately enable a boot device even though it's in the boot order. If that's the case, there should be a checkmark by the device in the boot order menu to show it's enabled.
Glass Packs--The sound of freedom.