How to Set BIOS to Boot from CD ROM or USB Flash Drive
Generic procedure:
1. Start locked computer, press Delete,or F2, or F10 key to enter BIOS interface
2. Then, find the BIOS setting menu, Then check boot device priority (sequence), it commonly shown as a list of devices, such as Floppy, CD-ROM, First Hard Disk etc.
3. At last, make sure check CD-ROM or USB Drive selected as a first priority boot device, then save and exit.
Note: Here below are 4 mainstream type of motherboards BIOS Setup procedure, check out that is relative of your locked computer to finish the BIOS setting task.
1: Set up AMI BIOS
This AmiBios Require you to press Delete 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 CD ROM or USB Flash Disk and second boot device to HARD DRIVE You can press F10 to save settings.
2: Set up Award BIOS
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 or USB Flash disk and Second or third to HDD-0 and Press F10 to save it.
3: Set up Dell BIOS
On some Dell Systems you can enter bios by pressing F2
Now choose Boot Sequence and then arrance 1 to CD-ROM or USB Flash disk 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
4: Set up Phoneix BIOS
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.
What is next?
