#1Back up your information to an external medium such as an external hard drive or a flash drive. The install process allows you to transfer current files to a fresh operating system (OS) install, but it is always best to be prepared with a backup of your files in case something goes wrong.#2Insert the first install CD or DVD of the operating system software.#3Restart your MacBook or MacBook Pro. Immediately hold down the "C" key as the computer reboots. This will cause your MacBook to boot from the CD or DVD you inserted.#4See the "Welcome" dialog that asks you to pick a language. It may also ask you to agree to the terms and conditions of the software install. Depending upon which OS version you are using, you might see the software perform several checks on your system. If you do not see this, do not worry.#5Choose where to install the OS. You're most likely going to select your primary hard drive. If you have one or more partitions on your hard drive, you can select any of them as long as they are large enough.#6Choose your install. You'll be presented with three options: "Upgrade," "Archive and Install," and "Erase and Install."Choose "Update" to simply update the current OS install on your MacBook. All your data, files and programs will remain intact.Choose "Archive and Install" if you need to back up all the data on your system and import it into a fresh install of the software. You will need to reinstall much of your non-Apple softwa