Nvidia has just attained Windows 7 WHQL certification for the latest 190.62 drivers, which enable DirectCompute natively within the Windows 7 OS - and that includes RC1 as well as the retail version.
DirectCompute will be distributed as part of the upcoming DirectX 11, but is fully supported by NVIDIA’s current lineup of DirectX 10 GPUs, including the G80, G92 and GT200 based products. Since it's API based and not CUDA, it also means that in time this technology will be available on ATI cards as well, but for now those with Nvidia hardware will get the first look.
The Windows7 OS uses the GPU like another CPU for certain highly parallel tasks - much like Adobe mixes OpenGL acceleration with CPU processing for its Photoshop CS4 and PDF version 9 and 10 products.
Nvidia also claims that functions like dragging and dropping video files onto portable players within the OS will automatically transcode them on GPU to make them compatible.
We wonder how the performance scales with the graphics card, but it must depend on the application: obviously video transcoding benefits from more memory bandwidth and stream processors, but simpler tasks like rotating an image clearly don't need much GPU horsepower.
Have you tried it? Let us know if you've seen a difference in the forums