I hope I'm wrong, but I think this one is going to be rough. Anyway, here's my build:
Mobo: Asus P8P67 LE
CPU: I5 2500k @4.3ghz
Cooler: Noctua NH-D14
Graphics Card: Galax GTX 970 EXOC
RAM: Ripjaws 4gb (x2)
SSD: Samsung 840 EVO 120gb (with Win 8.1)
HDD: Seagate Barracuda 2tb
PSU: Seasonic 520w 80+bronze
 Until 2 days ago, my computer was working just fine. When I woke up and attempted to turn it on, a message telling me to "select boot device" and press a key appeared.
 I attempted to restart my computer a few times and check my bios settings, but in most instances it said there was "no keyboard" and the "select boot device" message appeared yet again. But sometimes, it does detect it and it's possible to enter the bios menu after spamming del for a while.
 Upon succesfully entering the bios menu, I noticed that my HDD hasn't been detected either. Unlike my keyboard, there hasn't been a single time it was detected ever since this issue started. Oddly enough, I couldn't use my keyboard in the bios menu, which I did enter a handful of times, even though I had to press a key to enter the menu. On the other hand, my mouse works just fine at all times.
 I'd never used the EZ Flash 2 function before, but it's possible to see all folders inside my SSD without a problem if I use it. Of course, I can't open anything since it's part of the bios menu.
In other words, despite the fact my computer won't boot up at all, it's my HDD and keyboard that aren't properly detected as opposed to my SSD (where Win 8.1 is installed). Pretty odd. Ps: Both my HDD and SSD should be plugged in properly. I've double checked these cables to make sure they weren't lose.
On a side note, my SSD would make a clicking noise in short, regular intervals whenever I turned it on before this issue came up. I think it still did it a few times at first, but now it's like it's not even trying... no noise whatsoever.
 At one point, my monitor just wouldn't show anything. There was simply no signal. I tried rebooting a few more times, but soon I noticed the dram led on my mobo was red and decided to hold the MemOK button right next to it. After that, it went back to the previous "select boot device" stage (i.e. the same issues as before). One notable difference is that this time I was able to use the keyboard to navigate the menu... go figure.
 The last thing I did was remove the battery for 5 min to see if it would change anything at all, but all that happened afterwards was the usual date/time reset.
And that's about it.
The only thing that's happened somewhat recently that actually made my computer crash was when I spilled water over my mechanical keyboard. It stopped working properly and was typing all sorts of crazy stuff with a single key press. At one point, my computer restarted on its own because of that, so I immediately switched back to my previous keyboard, which solved the issue. I don't know if that could have anything to do with this, but I guess I might as well say everything I can at this point.
I'm really worried about this and it's such a pain to troubleshoot this sort of issue. What makes it worse is that I'd been planning to upgrade to Win 10 this month, something which I'd been putting it off to avoid any issues that might have come with the upgrade, but now this happens and... I hope everything will work out just fine. I'm scared though.
Please help!! I always feel extremely anxious whenever an issue like this occurs because it's much harder to fix it than when you have a regular computer. I'll be forever thankful!
Also, sorry for the length of my post.