CUDA doesn't see Geforce 9800GX2

SOLVED by following the post

Seems like only the LimitVideoPresentSoources is useful. I didn’t add the DisplayLessPolicy entry.

My computer has a Quadro FX1800 card and a 9800GX2 card. I intended to use the Quadro card to render the screen and use 9800GX2 to compute. But cudaGetDeviceCount returns 1 and only found the Quadro card. I installed the latest 195.62 driver and CUDA toolkit and SDK.
The OS is Windows 7 enterprise.

In device manager it seems one Quadro card and two 9800 card, which makes sense. GPU-Z also sees three cards but it reports CUDA is not enabled for the 9800 cards but is enabled for the Quadro card.

I tried enable/disable multi-GPU mode in the Control Panel but doesn’t solve the problem.

Does anyone have an idea on what’s going on? Thanks a lot.