FIXED: Closing MSI Afterburner solved this problem for me.

Everything is working except that I can't see the intro video but get sound and I can't see Doom 1 & 2 but get sound (demo's playing I think)

I get a blank light grey screen with the top right corner white for the intro video. On launching Doom 1 & 2 I get a blank area top right hand quarter of screen.

Have tried verifying cache and running the pre-installs manually. Changing screen resolution and full screen mode made no difference.

System specs: i7 950 @ stock, 6GB RAM, GTX 560 Ti 2GB, Driver 306.97

Did you install the directx version that comes with the game disk or did you install through Steam ? It might be a problem with not having an updated version of directX runtimes or could be you need to update your video card drivers -- try installing the microsoft directx end user run time package from http://www.microsoft.com/en-us/download/details.aspx?id=35 and then also download and install the newest version of video card drivers from Nvidia website and see if that helps.

Thanks for the reply, everything is up to date. It was MSI Afterburner causing the problem. Turning it off fixed it.