A Chinese website published a leaked slide with the system requirements of a GeForce GTX 280 graphics card.
CPU: NVIDIA recommends at least a Core 2 Duo E6300 for a single GeForce GTX 280 or GTX 260. To take full advantage of a SLI or triple-SLI system you'll need a Core 2 Duo E8500 or better.
Motherboard: GeForce GTX 200 GPUs work with any motherboard that supports PCI Express.
PSU: For a single GeForce GTX 280 GPU you need a 550W PSU with 40A on the 12V rail. For a single GeForce GTX 260 GPU NVIDIA recommends a 500W unit with 36A on the 12V rail. PSU requirements for SLI or triple-SLI setups aren't known. The GeForce GTX 260 needs two 6-pin PCI Express power connectors and the GeForce GTX 280 uses one 8-pin and one 6-pin PCI Express power connector.
Operating system: NVIDIA recommends that you update to Windows Vista Service Pack 1.