No power on, and no lights

I press the power button, it makes the power on noise, but no lights except the HDD activity light comes on. The fan runs at low speed, and nothing is displayed on the screen. I did reapply the thermal compound on this device a few months ago, as it was over heating, but it worked great up until a few days ago, nothing lead to this such as an update gone bad or anything.

My thought is the PSU (Power Supply Unit) or perhaps the motherboard are having issues. I've done some searching and some folks have said that one can adjust the output of the PSU, though I'm not sure how safe that would be, or even how.

Anyone else had this issues? Suggestions before I try a new PSU?