In a Mac

• 1). Put your boot disc in the CD/DVD drive. Press the power button to restart the computer and then press the "Option" key.
  
  
• 2). Select the "CD Start up" icon as your startup volume.
  
  
• 3). Click the right arrow to finish the selection, and then restart your computer again while simultaneously pressing the Command, Option, Shift and Delete keys. Your machine will finish booting from the CD or DVD.
  
  

In a PC

• 1). Put your boot disc in the CD/DVD drive.
  
  
• 2). Press the power button to restart the computer. Most newer PCs are configured to boot from a CD, but if yours isn't then you'll need to go into the CMOS setup (also known as BIOS) to enable this function. Your starting screen should tell you which key to press to enter Setup; in newer machines it might be the Delete key (Del) while in older models it could be the F2, F6 or F10 keys. In the CMOS setup, go to Boot Screen Options and select the disc drive as the main boot source. Save and close out.
  
  
• 3). Restart the computer. It should now boot from a CD or DVD.