Put in your original OS X install DVD that came with your computer. Restart the machine, hold down C during restart to boot from the DVD. Choose to install OS X, and "Archive and Install" will be one of the options. Make sure you choose to preserve your user files and settings.
On a side note, keep in mind that Archive and Install will NOT install 10.4.9, it will install the version from your DVD (probably 10.4.6 or 10.4.8, depending on when you bought the computer). In order to upgrade you will have to find the upgrade file and download it from Apple.com. You will NOT be able to download 10.4.9 from the built-in Software Update, as it will automatically try to upgrade you to 10.4.10. Hope this helps you out.