If you don't have the install package that shipped with this Mac when new and if not Tiger and you purchased a Tiger retail install package to upgrade the OS, you need both install packages.
The original install package includes additional software provided by Apple for this Mac model that is not included with a Tiger retail install package.
You need the original install package in case you need to reinstall an individual application only without having to re-install the entire OS, re-installing the entire OS and all included software via an Archive & Install or an Erase & Install and last but not least, the ability to run Disk First Aid repair via Disk Utility on your hard drive or boot volume.
Regardless what your actual intentions are, you need to get your hands on a replacement install package - the original install package that shipped with this Mac when new which is model and build specific.
