Monitors turn off and every system fan goes full speed

Hello!

I'm typing this as quickly as possible so I can get this up in time before my pc dies again.

For no specific reason, my custom-built computer will just shut off the monitors and then every fan goes beserk. This happens during no specific task. Whether it be playing a game, typing a document, or just watching a youtube video. The power supply makes the most noise, and I've run diagnostics on every hard drive I have. I've also scanned for viruses, too.

This all happened after I came back from vacation. Keep in mind that I was gone for 6 days with no issues prior to returning; I came back, turned it on, and played some Metro Last Light and all of the sudden, it just happened. I have no idea what's causing this and the longest it has gone without going crazy is around a hour.

Thanks in advance.

Not sure if it matters, but I got a new keyboard for christmas. Not sure if it's the problem, but I'm trying it out right now.

Keep in mind that I was gone for 6 days with no issues prior to returning;

I'm thinking the 'long' inactivity was an invitation to critters to nest in a new home.

When monitor turns off, that's usually a graphics card's response to trouble.

When fans go full speed, temperature is too high.

Pest control needs to look inside the box to see if some component is not right, ex. fan not spinning or card too hot.