Insert the CD into your computer. To do so, place the CD logo side-up in your computer's CD tray. The CD must have a version of Windows on it.
Open Start. Do this by clicking the Windows logo in the bottom-left corner of the screen, or by pressing ⊞ Win.
On Windows 8, place the mouse cursor on the top-right side of the screen, then click the magnifying glass.
Click. It's in the bottom-left corner of the Start window.
Click Restart. This option is near the bottom of the pop-up menu.
If you have programs running, you may be prompted to click Restart anyway before you can continue.
Press and hold Del or F2 to enter setup. This key may also be a different key. Most computers will display a message on startup that says "Press [key] to enter setup" or something similar, so look for this message when your computer restarts to confirm the key you should press to access the BIOS.
Consult your computer's manual or online support page to confirm your computer's BIOS key.
Navigate to the Boot tab. You'll use the arrow keys to select it.
The Boot tab may instead say Boot Options, depending on your computer's manufacturer.
Select the CD-ROM Drive option. To do so, press the ↓ arrow until this option has a box around it.
Press the + key until CD-ROM Drive is first. This will place it at the top of the boot options list.
You may have to press a different key as indicated by the key legend on the far-right side of the BIOS screen.
Save your settings. You should see a key prompt (e.g., F10) at the bottom of the screen that correlates to "Save and Exit"; pressing it will restart your computer, using the CD drive as a reboot point.
You may have to press ↵ Enter to confirm the changes.
Insert the CD into your computer. To do so, slide the CD logo side-up into the CD slot on your Mac. The CD must have a version of Mac OS on it to qualify as a boot option.
Some Macs don't have CD slots. If your Mac doesn't have a CD slot, you'll need to purchase an external CD drive.
Click. It's in the upper-left corner of the screen.
Click Restart. This option is at the bottom of the Apple menu.
Click Restart when prompted. Doing so will cause your Mac to begin restarting.
Hold down the ⌘ Command key. You'll need to hold down ⌘ Command as soon as your Mac begins restarting and keep holding it until the Startup Manager window appears.
Click the CD icon. It will typically say something like "Mac OS X Install DVD" below it. Clicking this icon selects it.
Press ⏎ Return. Doing so will prompt your Mac to boot from the CD drive.