So follow up to my last post (in a nutshell bought dell optiplex 9020 off Facebook worked just fine then took hdd bay out plugged everything back in how it was before hen no boot error message then accidentally unchecked a box that said something like allow legacy settings at bootup or something then now I have no display at all) my power button and all the lights turn on, I replaced he cmos battery still no display, chnage the gpu or replace motherboard? I have no idea I need help