Possible the powersupply. But unlikely. Id have to say it might be something like.. Bad ram. Or your moniter just sucks. Or your graphics card. First thing to do is to hook your computer up to another moniter and see what happens. If that clears, take out the graphics card, and disable it in BIOS. And if thats still not the problem, chage out some ram, try it in different slots ect. And if all else fails.. Get a new computer
Anyways.. Welcome to CF dude!