graphics cards and power supply

just because it says 400W recommended it does not mean that it requires 400W, though I do not advise anything less then 300W of high quality, your Power supply is certainly not sufficient enough to run that card. Anyway I doubt that power supply can even deliver 255W in the first place, and most likely has very low amps on the single/dual 12V (total) rail.


As for part 2 of what you asked - Constant blue/black screens as your system will constantly be crashing once the power supply reaches it's output limit. Worst case is it blows up and throws ultra high dangerous currents through your system and you lose components as a result.