Dead hard drive, now the screen is blank? Please help.

So I followed the guide, which was pretty awesome, and replaced a dead hard drive. After buttoning it up, I then had to open up everything again and to get a bad disc out of the optical drive. So, having done all that, black screen on startup. No sound, no anything. I can't insert the system disc in the optical drive for some reason. I don't think I wrecked the optical drive but I may. But my bigger concern is the blank screen. I was pretty methodical digging into this computer and I'm fairly sure I re-connected everything as it should be.

So, any ideas why the display would appear to dead? I can hear the new HD spinning up. Every once in a while I can some noise from the optical drive but no other sign of life.

Is there some common mistake made by idiots (that's me) that I might check on? Any help would be greatly appreciated. Thank you.