Computer Will Not Boot

I have a computer given to me that has a mysterious issue. Try to boot, no post beep, black screen nothing to be seen at all, not even a flicker. I was told by the previous owner that all they did was to plug in a printer to USB port at the back, tried to install using proper driver, then the computer locked up and was unresponsive. The reset button was pressed and from that point, nothing but black screen. All the fans and hard drive spin.

Have tried:
New powwer supply
clearing the CMOS
reseating the RAM and CPU
new RAM