You will need to ensure that the DVD drive is either designated as first in the boot sequence (followed by the Windows boot Partition /Drive) or use a startup menu (varies by System) to select it to boot from DVD on this /the next occasion.
A bootable windows 8 or 10 disk will contain the correct security files /EFI folder or partition for Secure boot that a bootable programme disk must have for most modern BIOS'es to load/run it. (If not {e.g. early windows 7} change BIOS settings to temporarily choose No in Secure Boot section or Compatability mode in Boot settings
If that all fails copy the entire windows disk including any hidden partitions to a USB drive and see if you have better luck that way. With a valid licence you can download a bootable USB stick or make a DVD iso file on the windows support website.