More than likely this is a PSU problem. However it could be a number of components causing this problem. I would start by doing exactly what the gentlemen above me have stated. Try a different PSU if you have one available. If the same problem persists than it may be a motherboard problem. If this is the case then you may need to take it to a local shop and test another motherboard unless you happen to have one lying around (I know I sure don't). Hopefully it's a PSU problem.