Dell - Dimension 5100 - No Power; to solid Amber Light; and back.

Hello everyone, I've run into a crippling problem with my Desktop PC, a Dell Dimension 5100.

First let me tell you that I am only moderately computer savvy, and that's generous. I know basically what parts are what, where they go, and what different parts will work with each other etc.
 
Ok, so I was playing a computer game the other day and the computer suddenly froze. I had mouse control initially, but sound was skipping and the image on the screen was frozen. I tried alt-tabbing and just terminating the game, but that in turn made me lose mouse control so I figured I would just shut it off and reboot. I held the power button down for what seemed to be 5 mins and it wouldn't shut off, so I unplugged the power cord from the back, and my troubles began.

I initially thought it was the power supply that had fried, so I opened it up, took the PSU out, and tried the paperclip test, and it passed (is this as verifiable as I think it is? I put a paper clip in the green wire pin, and a black wire pin and it the PSU fan started blowing for as long is I had it powered.) So I am not sure that the PSU is actually the problem, the scanning the internet for comparable problems seems to indicate that it very much could be. Also, I always make sure to discharge static before I touch the inside of any computer. So I put that back in and retried, still no power, no indicator lights on power button, nothing except for the solid green light on the motherboard. I tried taking out the CMOS battery for a bit, after holding down the power button for a bit also. And nothing seemed to happen. I read that the front I/O panel might be malfunctioning somehow, or 'shorted,' but I dont really now how to check for that. I made sure it is isolated from everything else, not rubbing any metal etc., would that prevent it from doing so? I have a spare, inoperable, Dell XPS, so I tried removing the I/O panel from that to replace it, but low-and-behold they are different sizes. I checked all connections, cleaned out all the dust, removed all RAM except for slot 1, and still nothing. I read in a forum somewhere that someone that had the same problem left his or her computer connected to power and sitting, and that over time it booted up no problem. So I did just that, and noticed a few hours later that fans were running and the power button was illuminated solid Amber, which it still is. So I read up on that situation, and someone somewhere mentioned that a CMOS reset might fix it from there, so I unplugged everything and tried the battery reset again, and was not surprised to find out that after reconnecting power and video cables, it was completely dead again, no indicators except MOBO green, and no beeps when starting up, and no video whatsoever. So I replugged in all cables and let it sit, and a couple hours later noticed it was running fans again, with solid amber indicator. Sorry for being so painfully detailed, but I wasn't sure if the steps I took would be helpful in diagnosis.

At this point I am now led to believe it is either a bad motherboard (does a solid green light debunk that?) or the front I/O panel. It is currently in Fans on mode, with solid amber indicator.

Thank you guys so very much for any help, it is genuinely appreciated!