This is actually a pretty common problem that has recently become more complex.
Your computer’s BIOS needs to be instructed to check for a bootable CD or DVD before it tries to load whatever is on the hard drive. Right now, your computer is configured to either ignore the CD/DVD at boot time or check the hard disk first.
Oh, you don’t have a BIOS? You have a newer machine running UEFI?
Well then things get more complex.
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UEFI and Secure Boot
UEFI, an acronym for Unified Extensible Firmware Interface, is a new type of BIOS that includes several enhancements. One of those is something called “secure boot”.
Secure boot matters because there’s a glaring security hole that’s been present in almost every PC since day one, and it’s very simple, and very powerful:
In fact, I often leverage this fact when people have lost their system administrator password. I’ve lost the password to my Windows Administrator account. How do I get it back? is an article on Ask Leo! that walks through the steps of resetting the administrator password by booting from a CD-ROM with the appropriate tools.
Secure Boot, when enabled, prevents this from being possible. It can prevent changes in the boot order, and it can restrict booting to only “official” boot images.
Windows 8 is the first version of Windows that can take advantage of UEFI and Secure Boot. That means that if your Windows 8 system has UEFI and has Secure Boot turned on, then it’s very possible that in order to boot from something other than the hard disk you’ll need to turn Secure Boot off first.
Turning off Secure Boot
Click on the power option (either on the Start Screen or the Charms Bar) and then hold down the shift key while clicking on Restart.
This will reboot into a “Choose an option” screen:
It’s possible that on some machines you may be able to reboot from a device such as a CD or USB drive by clicking on Use a device at this point. I recommend you give it a try at least once. If it works, no further changes are necessary.
Assuming that it does not, click on Troubleshoot.
And then click on Advanced options.
I can’t show you what comes next, because it’s different from machine to machine.
If your machine uses UEFI and Windows 8 recognizes it, there will be an additional option on this screen: UEFI Firmware Settings. Click on that to be taken to the UEFI interface for your computer.
In that interface should be the option to disable Secure Boot. You may need to check your computer’s documentation for the specific location within the interface.
Changing the boot order
Like the BIOS before it, UEFI also controls the boot order – which devices the computer will look to boot from first.
Look for the settings to ensure that the USB or CD/DVD drive is earlier in the sequence than the hard disk, so that the system will boot from your recovery drive before booting from the internal hard drive.