An "Archive & Install" will get you close to an "Erase & Install". This
saves your data. You might have to enter some registration info again, but
all in all it's pretty painless.
Archive and Install
1) Insert the Mac OS X Install Disc and double-click the Install Mac OS X
2) Follow the onscreen instructions. In the pane where you select the
destination disk, select your current Mac OS X disk (in most cases, it will
be the only one available).
3) Click Options. If you want to save your existing files, users, and
network settings, select rchive and Install,and then select reserve
Users and Network Settings.If you want to erase everything on your
computer and reinstall Mac OS X, select rase and Install.You can
recover erased data.
4) Click Continue.
5) Click Customize to select which parts of Mac OS X you like to install,
or click Install to perform a basic installation (recommended).
Once the install has finished, your system will be at whatever level the
disk you have is. So if your Install DVD/CD disk is 10.5.0, that's what
version of OS will be on your Mac. You will need to download the appropriate
Combo Updater from Apple's site to restore the system to a higher version.
After you run the combo, allow Software Update to download and install any
Since you are new, read this page about the different types of installers.
I have a few tips and links posted to help new users here: