I think that screen saver only runs on machines that support Quartz Extreme graphics, which basically means at least a 32mb graphic card. I don't know what graphics card the G3/400 had, but it most likely isn't supported. It looks like Apple provided a clever way of hiding the option if you don't have a supported graphic card.
- iMac G5 1.8GHZ 17" | SuperDrive | 160GB | 512MB | Airport Extreme | Bluetooth Keyboard & Mouse | Wacom Intuos II
- Pentax *ist DL - JVC MiniDV Camcorder - Airport Express - iPod Nano 1gb white