According to Nvidia, the new Geforce 352.63 Beta drivers are the latest recommended drivers for all pre-release Windows 10 testing.
According to the release notes, Nvidia's newest WDDM 2.0 and DirectX 12 ready drivers support only Geforce 900, Geforce 700 and the Geforce 600 series, including Geforce GTX Titan graphics cards on the desktop side as well as Geforce 900M, 800M, 700M and 600M series graphics cards on the notebook side.
Weighing in at 327.06MB, these new drivers are available for both Windows 10 64-bit and 32-bit OS.
As always, you can find the Geforce 352.63 Beta drivers at Nvidia's driver support website.