Okay heres the deal. My monitor suddenly stopped working. PC still powers up, yet my moniter doesn't. I have to mash the power button several times before it then temporarily displays "Video input not detected. Please check cable" on a black screen.

Initially I thought it could have been the vid card (ati 9550 agp) so I switched the vid cards to an nvidia that I used to have, and the problem persisted. So then I thought, okay I'll try my monitor on my ma's computer and it seemed to work, so that ruled out the moniter itself. My next thought was that it could have been my mobo (msi k8n neo2 nforce3) so I switched that, with an intel board and different cpu. Hooked it up, and I got the same thing, "video input not detected." So I took my mothers' moniter and hooked it up, and again the same damn message.

At this point I am completely baffled as to what has caused this, and why it still persists when I essentially have built an entirely different computer. I have used multiple configurations with my ram sticks to eliminate the possibility of bad ram, and yet nothing has changed. If it's not my mobo, or not my ram, or not my gpu, or not my cord, then it must be my moniter, right? Yet my moniter works fine on other pc's. What else could it be? Thanks in advance.

Your PC is not powering up for one reason or another...it's not the monitor as you have mentioned.

That is the error message you will get on a monitor when your system isn't posting...so something has died for sure other than the monitor.

You swapped just about everything but the power supply and HD it sounds like.

The power supply is the most likely suspect here...a pc will stil display a post message if the HD is toast or the SO is corrupt.

Could be that one of the other rails besides the 12v is dead (3.3v or 5v) the 12v rail would still make the fans and LED's come on and make it apear as if the system SHOULD be able to boot, but won't.