My first thought was that the fan had become dislodged, that's a pretty common issue. The noise was coming from the PSU, only thing in there that moves is the fan. Pretty easy conclusion. So, I take it apart enough to look at the fan and it's pretty gross. I cleaned it up, along with some other parts of the interior of my desktop.
Unfortunately, I didn't see anything wrong. I ran some tests (turning the computer on while I had the PSU in different positions). Nothing really worked, so I took the fan out, remounted it, and tested again. It was making a much lower sound, which I took to be a good sign. I had full intentions of using it as it was and put it back into the case, reconnected everything, and turned on the computer.
Of course, it started grinding again. So, as of right now my development machine is out of commission. Which means that all development ceases until I can afford a new one. What's worse is that I'm supposed to be saving my money for computer science certifications and school, but I guess I now get to spend money trying to fix my computer so that I can actually go back to programming and actually having a good machine to do things with.