I have traced the source of my grainy pictures to Media Player Classic. I think it is only when I play a DVD I have make from my hard drive recorder (Movies I record from TV). Captures made from DVDs I have bought are OK. If I play the recorded disc in another program it appears much clearer than if I play it in MPC. Is there a way to adjust the resolution of MPC to give clearer captures?

you can try to change some settings in options (view->options) : on the "output" page, I use "VMR7 (windowed)" as setting for DirectShow video.
Except that, I do not know what could cause problem.
Which version of MPC do you have?

I had 6.4.9.0 but updated to 6.4.9.1 with no difference, maybe it is the way my HDD recorder converts to DVD. Will try adjusting settings in MPC as you suggested.

It was just to be sure that you didn't have a very old version, as they improved quality of captures some time ago.
About adjusting that setting, to make the test be sure to close and reopen MPC after having changed the option, as I am not sure that it is taken in account directly.