help PC won't Post

[Imitheos]

    For awhile now, I've been running an old HP Pavilion with some upgraded parts. Yesterday, when powering on the system, I was greeted with a blue screen, and the error code, "memory_management," Preventing me from getting to the OS. Assuming this was the RAM, I decided to pull the GPU (in the way of the ram,) and reseat all 4 sticks. This time powering it on, no screen was displayed. The fans spin, and the lights turn on, but nothing more. I've had this problem before with this system, however, and was able to fix it by simply reseating the graphics card. But no matter how much I try, reseating, swapping GPUs, monitors, cables, I get nothing. Thinking back, when I first got the system, (used,) it had the same issue, assumed it was the psu, I replaced it. Everything seemed to work again, until now. If it's not the psu, or the GPU, it must be the motherboard, right? If anyone has suggestions, or experience with this sort of issue, I'd be very appreciative.

 

Specs:

Amd Phenom x4 840t

Amd Radeon RX 570

128gb SSD

1Tb HDD

750w Thermaltake PSU

24Gbs ddr3

 

Thanks.