Windows media player cannot play the video because there is a problem with your video card

Hi,
When i am palying any DVD/ movies on my notebook with OS Windows
vista home premium, i am getting an error as "Windows media player
cannot play the video because there is a problem with your video card"
when i click on "web help" button i am geting the error code
"C00D10BD". In net it is given that this will be fixed by installing
DirectX, but when i am try to install it, i am getting one more error
as "A cabinet file necessary for installation cannot be trusted.
Please verify the Cryptographic Services are enabled and the cabinet
file certificate is valid." Could you please help me out in this
regard?

Regards
ranjit bhumula