All modern Computer Systems manufactured in the last years, support boot from cd feature, but it may be required to configure this feature in bios or previous owner of your computer system may have disabled this feature or may have changed the boot priority sequence ).
When you start your computer, check the boot-screen for setup key, In most newer pc it will be DELETE key, so make sure to check it.
This AmiBios Require you to press DEL key to enter setup
now you will see some similar screen and choose the BOOT option and choose Boot Device Priority and choose first boot device to CDROM and second boot device to HARD DRIVE You can press F10 to save settings.
On Award Bios you will see some similar screen and choose the right key to Enter setup
Now choose Advanced Bios Features
and set First Boot Device to CDROM and Second or third to HDD-0 and Press F10 to save it.
On some Dell Systems you can enter bios by pressing F2
Now choose Boot Sequence and then arrance 1 to CD-Rom by pressing - + and press space to enable it, Press ESC and choose save settings and exit.
On some Dell Systems you can enter bios by pressing F2
Sometimes you can press F12 to temporary boot from cd on some Dell Systems.
Press F2 to enter bios setup
and set Boot Sequence to A,CDROM,C and Press Esc and then F10 to save it.
Some Computer has Option to temporary boot from Cd/Hdd/Floppy/Usb Device, Just keep tapping the F8 button to get Boot Menu and Now choose your manufacture of CDRom.