Will the Asus GT440 work in a Apple G5?

http://www.asus.com/Graphics_Cards/NVIDIA_Series/ENGT440DI1GD5/#specifications|||Not a chance in hell. Even if you have the Powermac G5 with PCIe slots ("Apple G5" is hardly specific), it still wouldn't work. Assuming you have a tower, you must find specifically Mac-compatible cards or specific PC cards that can be flashed with a Mac ROM.