It sounds like you wiped your factory installed Tiger installation and re-installed using a retail copy of Tiger. Is that right? If so, you need to use the install disks that came with your computer to reinstall Tiger, or use a utility like Pacifist to extract the iLife packages from those disks and install them into your current application.
iLife is provided with new computers, not with the OS. That's why a retail copy won't have the iLife applications, but the original install disks will.