Black screen at startup, fans slow down to a crawl

Hello! I recently came back from a trip out of town and have been experiencing issues with my computer. I made sure to leave the power cable unplugged before I left. Now, whenever I turn the PC on, I get a black screen with no sound at all, and after a few seconds all the fans slow down to a crawl, making an almost imperceptible noise. When I turn the PC off again, the PSU fan keeps spinning and my mouse's light is still on.

I can't access my full specs until I can open up the thing, but what I do remember is:

- Phenom ii x6
- Geforce GTX 760
- 8gb ram
- running Windows 7 64-bit

The PC was working fine before I left, what's going on now? I will update the specs when I get back from work. Thank you for your help.

 

Solved it! Apparently my PSU was having issues. After cleaning off the dust with a soft brush, it worked for a few hours before shorting out and scaring the crap out of me. Switched it for a new one with higher capacity (just in case, I don't think the issue was overloading but I wanted to be sure) and it's working fine again.