My DVD drive has stopped playing DVDs.

I have an ATI video card and have ATI multimedia center
installed also interactual player.

When i run the ati multimedia center diagnostics tests  
for DVD compatability it produces errors in two places, it
says,

Direct X 8.1 or higher not installed ( it is and is
working fine otherwise )

and...

WDM not installed. I reinstalled this from the ATI driver
CD.

Please advise anyone, I would also like to try and
uninstall Direct X 8.1 and reinstall it but I am not sure
how to do it.