Flight Simulator X Problems?

I own an Hp Pavilion zv5000 with graphics by ATI and I installed Microsoft Flight Simulator X but it was nohere near what I tought it was going to be! It was VERY SLOW and the graphics where horrible! I installed the service pack and it didn't do squat! I set all the settings to high and that just made it worse! My computer meets all the requirements but it is syill crap!