|Are you using a new or recycled hard drive? Post the specs on the hard drive. Also post the model of your power supply.|
Also appears you are mixing brands of RAM which may run at different speeds, voltages, etc.
To eliminate other hardware you should bench test the board outside the case. Power supply, motherboard, CPU/HS/fan, integrated or add in graphics, 1 stick of RAM, wired keyboard, monitor.
NO other hardware and not case to board connections. Connect the main power connector and the CPU and graphics auxiliary power connectors ONLY. No other add in cards. No USB devices except for keyboard if necessary, No drives, mouse, printers, scanners, cameras, etc.
Start the system by temporarily shorting the 2 power switch pins on the motherboard. Enter the BIOS if you POST and let it set there for at least a couple of hours. Check the temperatures and voltages while in the BIOS screens.
50c is too high for an idle temperature. Redo the paste after cleaning off all old paste.