Original post : Booting from a CD or DVD.
Running Windows 8 or using a UEFI PC/laptop?
Newer Windows PCs and laptops use something called UEFI/EFI that can interfere with booting from recovery CDs and USBs. You may need to follow the additional instructions on enabling Legacy Boot and disabling Secure Boot to make sure your PC or laptop is configured to support booting from recovery CDs, DVDs, and USB sticks, especially if you can't get it to work after following the steps above.
Remember to change the option back!
If you had to change the device priority in your BIOS, you will need to remember to change it back once you're done with the recovery/installation disc. Otherwise, your PC will always boot from the CD/DVD drive if there's anything in it — and only if there is no bootable CD inside will it actually try booting from your local disk!