When you buy a computer, the default settings in the computer’s BIOS generally tell the computer to boot to the built-in hard drive first. This allows your computer to read and boot to the installed operating system. Occasionally, however, you may need to boot to a disk instead. For instance, if you need to repair or reinstall the operating system on your Acer Extensa 5210 laptop from CD, you must override the computer’s setting to boot to the hard drive to boot to the installation CD instead.
Power on your Acer Extensa 5210 laptop. If your laptop is already on, go to the “Start” menu and “Restart” to reboot the system.
Watch for the message to appear on the screen as the system boots up that says, “Press <Alt>+<F10> to enter set-up.” Press the “Alt” and “F10” keys simultaneously to enter the BIOS of the Acer Extensa 5210 laptop.
Arrow over to the “Boot” heading on the screen and press the “Enter” key to make the “Boot” feature active in the BIOS. Arrow down to “Boot Device Priority” and press "Enter" to make it active. Press the right or left arrow to change the device to “CDROM” and press “Enter.” Arrow down to “2nd Boot Device” and press “Enter,” and then use the right or left arrow to select “Hard Drive” and press “Enter” again.
Use the right arrow to move over to the “Exit” option at the top of the BIOS screen and press “Enter.” Once you have exited the BIOS, insert the CD that you want to boot to into the CD drive of your Acer Extensa 5210 laptop and restart the computer. The Acer Extensa 5210 boots to the CD and only the CD set-up appears on the screen.