rome total war crashes at startup?

i dl rome total war demo , i really want to play this looks good, but on startup my montior turns it self off , with the light flashing and , other time it just crashes frezzes the screen.

i dunno wot to do also comes up with error report for my ati 9700 pro [the driver for this display was unable to complete a drawing operation] the driver seems to be responsiable for system instability etc.