Seems most of the people who've had problems running the C.P.C. demo use certain types of Nvidia's Geforce cards and I think it's causing issues with the surface technique used in the game to get clean non-blurry pixels in fullscreen. Until I can fix this and get it confirmed (difficult when you don't actually have access to the hardware mentioned). I've got a couple people now on my MSN who have these video cards and when I've got a clear head I'll try some work-arounds.
It also seems there is an issue with running the game on Windows 7 RC. Perhaps the Geforce workaround will work for that too. I don't know. I'm gonna need to think of something since all my projects use the same technique.