All fans spin, nothing happens

Hardware Hub Motherboards
1

So I'm building a Pc from spare parts for my sister and it just stopped working when I thought I was done. Booted up, everything was fine, worked wonderful. Shut down, want to unplug everything to get the Pc over to my sister. When I pull the power cable from the back of the Pc I notice that a fan was still running even though the Pc was off. Want to investigate, plug it back in and now the Pcjust wont work anymore, when turning power on all fans turn on and wont stop spinning anymore, gpu, cpu, psu. The power&hdd leds of the case dont turn on tho (except for occasional blinking power led, wtf) and the cpu fan goes to full load every 30 seconds and then goes back to a more reasonable speed. I dont get a signal to my monitor, usb devices dont seem to get power and the led next to the lan port doesnt turn on aswell. I dont have a fucking clue what is going on, all front panel connectors and everything else appears to be plugged in correctly but I cant really get a reaction out of it, except for a bit of blinking from the power led and the cpu fan ramping up when I press the power switch, both of those dont always happen and I cant work out any pattern.
The way everything is plugged in right now worked just fine and now it doesnt.
Specs:
I5 2500k @Stock with stockcooler
Msi gtx 550 ti @Stock
6Gb Ram
Medion ms7728
Some 450w fsp power supply
A 2.5 inch 320gb toshiba hdd i pulled out of a broken Asus laptop
Sharkoon Vs4-V
It runs on 64bit Win10 if that matters.

I tried turning the power and reset switch connectors, in case i somehow messed up the + -, I used the front panel connectors of another case (define r5) and just got the same, fans spinning, leds blinking, power switch not doing what its supposed to.

Edit: monitor is connected via hdmi but vga didnt get a signal either.

2

remove motherboard battery - unplug power cord - press power button for 5-10 secs, put battery back in, connect power cable, start pc

step 2 if above wont work: remove non-mandatory hardware, such as HDD, ram (leave 1 stick), gpu (should startup without it), disconnect extra case fans

3

ps: there is probably jumper to reset bios, i prefer this technique tho

ps2: if your power supply has power switch, you dont have to disconnect it

4

See if it posts with a different power supply. If it's still not booting start disconnecting stuff from it and keep going till you get to the bare minimum. If it's still not posting put it on a cardboard box and give it a last try. If it's still acting weird with only the CPU, a stick of RAM placed on a box I think you're out of luck mate.

5

I tested everything on my own Pc and it seems like the mobo died :(

6

are you sure all standoffs in case are on correct places, not shorting motherboard? Had similar problem at work when boss built pc...that wasnt booting up, guess why... :D

7

It worked perfectly, without touching it in the slightest it went to hell. When I put it into the Fractal case it did the same thing. Seems like I'm out of luck :(