My mac computer was working fine but I took the hard drives out of it and formatted them with my new computer. Now when I re-insert the zero-filled drives the monitor is just perpetually black. I tried using the original graphics card that came with the Mac Pro (8800 GT) but that didn't work (even though I know the card works) and even tried another graphics card I know works but that didn't work either. I took out all drives but the first one, all ram but 2 sticks, and even tried other monitors that I know worked. Nothing. I tried resetting the NVRAM, holding option during boot, apple hardware test, and booting from the CD. No picture on the monitor for any of those attempts. I know the computer works because it was working fine before I formatted the drives. Also it responds to keyboard input like holding F12 during bootup opens the tray and holding command option p r I can hear the mac chime twice. The only thing I can think of is maybe the bootloader is screwed up. Like 5 years ago when trying to set up a tri-boot I was messing with the bootloader. If this is the case is there any way to fix it? Where is the bootloader stored? Can it be reset? Thanks for reading.