Hello,
I am still in learning Houdini, I don't know what I did. but when I put lights it doesn't show the shadow. I turn on the shadow to point quality
and even worst when I enabled spot light on the light. everything is black.
I have my graphic card on Nvidia quadro 880M

Can someone help? Thanks

If you're referring to viewport shadows, and are using the nvidia driver 319 or up, you need to be running at least Houdini 12.5.412 to get a workaround for a driver issue that broke viewport shadows.