While it is wise to backup your personal files, it is just as important to backup all the rest of the important data on your hard disk. There are plenty of backup options you have. For example, you can backup your data on a CD, DVD, external hard disk as well as at an online storage service. The things you can backup could be your personal files that are located in your home folder that may contain important documents, pictures, movies, applications, etc.
Decide Install Type
There are two reinstall types of Max OS X. Each of these is used for a different purpose. Therefore, before you proceed to reinstall, it is important that that you are aware of the differences between each install type.
Archive and Install
This type of install is available only in Mac OS X 10.2 and later. Select this option if you want to install a fresh Mac OS X on your computer. Archive and Install automatically moves (not copy) current system files to a folder “Previous System” then begins the Mac OS X reinstall process. You can also select Preserve Users and Network Settings if you want to import your existing user account and network information and personal files into the new system.
Note: If OS X does not already exist, this option will not be available.
Erase and Install
If you choose Erase and Install, the whole contents of your hard drive will be erased before reinstalling Mac OS X. This is the fastest way of reinstalling Mac OS on your system and because it erases all previous settings and data, it may take a little time to set up the computer after installation.
Reinstall Mac OS X
1. Insert your Mac OS X install DVD into the DVD Drive.
2. Restart your computer and hold down the ‘C’ key while the computer starts up and soon you will see a green screen.
3. A welcome screen appears you can select your choice of language there. Click on the Continue button, the Important Information window will open.
4. Click on the Continue button and you will see the Software License Agreement on the screen. Click Agree if you agree to the license agreement. The Select a Destination screen appears.
5. Click on the volume you wish to install Mac OS X to.
6. Click on the Options button, you will see the installation options on the screen.
7. Select the install type. (If you choose Archive and Install, then also select the volume which already has Mac OS X installed)
8. Click OK and then Continue to start the installation.