Was the PSU powered off when you swapped the modules? I presume that the known good module doesn't work either? Have you removed and reinserted the video card (unless you use an onboard GPU)?
Uhh no, I haven't tried to remove the video card yet. I'm not sure if I can pull it out without having to unscrew it and my experience with hardware is limited. I have an ATI HD 5700 GPU, its not inbuilt into the motherboard. When you say 'modules' I assume you mean the Ram Sticks? Yes, I unpowered the tower before removing the ram sticks and I didn't break or bend them either.
-edit- The Keyboard and Mouse won't power up either, so its not just the monitor. I just cleaned out my GPU which was very dusty and put it back in, it didn't have any effect when I started the computer again.