Aurora R1, Won't Boot

Hello,

The other day, a friend of mine gave me his old PC, an Alienware Aurora R1. I tested it out, and it worked fine, cleaned it, tested it out, still worked. After I was 100% sure it worked, I shut it off and went to sleep. The next day I was unable to turn it on. I figured it was due to the flakey power button mine had, which was loose anyway, and so I removed it and tried again. Still nothing. It even got to the point that I removed the front bezel and manually pressed the button. It still didn't work. I doubt it's the PSU, as not only does the red "POWER" light come on internally, but the PSU test button works fine, and starts up all the fans. The only thing I can think of that I messed with was removing the memory fan, as it was broken. I uploaded a video of it here to demonstrate the issue. Any help is appreciated!