PC won't boot, fan starts and then stops

What a nightmare, I posted yesterday about issues with my PC when my hard drive stopped working, I went around in circles on BIOS until finally I managed to find a way to update BIOS that allowed my new SSD to be seen. Great I thought. But then, when the HDD loaded my backed-up EASEUS Windows file (which I put on the drive from my other PC) it came up with a windows style light blue screen (sad face) error that it can't boot. No big deal I thought, maybe I just need to set the MBR or something. So I turned off the PC and went to find a MBR tool on my other PC. Now when I turn on the PC it won't even get to BIOS, my monitor turns itself off and the CPU fan cuts out after 5 seconds. Please see video below for what happens.

These are the things I have done or tried............

1. I removed the CMOS battery, waited 10 mins, and inserted a new one. No change.
2. Removed PCI cards and then tested one by one, no change.
3. Removed ALL PCI cards at once, no change
4. Removed ALL HDDs, no change
5. Left in just 1 HDD, no change
6. Tried each memory module, one by one, in the main socket nearest the power connector, no change
7. Tried a PC analyser PCI diagnostic card, shows code 00, which says in manual "Code copying to specific areas is done. Passing control to INT, 19h boot loader next".
8. Gigabytes own motherboard LED shows "32" which says "CPU PEI initialization" in the manual.
9. Tried a PSU tester, all voltage numbers are fine and correct. Unlikely to be the PSU, but who knows.
10. Tried internal graphics card port in case BIOS reverted to internal graphics, no change.

So what the hell can it be ? Sadly I don't have a PC speaker, so I can't tell how far boot gets, but I know the HDD makes a noise on boot and also there must be some kind of graphics signal because when I remove the DVI socket out of the back of my PC my KVM changes to my other PC, which happens when my PC is turned off. So it is recognising when the graphics is removed.

I doubt all 4 memory modules could go at once. So I suppose I can rule out that, and my PSU. Which leaves the motherboard or CPU. But the motherboard code, or the PC diagnostic card, doesn't seem to be very definite with an error.

Please see Youtube video here of what happens when I turn it on : YouTube

PC age : 2012
Motherboard : GA-Z77X-UD5H
CPU : Intel i7 3770K Ivy Bridge with Be Quiet cooler
Memory : 16gb in 4 modules
PSU : Coolermaster 700 watts
Graphics : Fairly modern budget AMD Radeon (possibly 560rx, can't remember)
Bios : Dual BIOS, latest BIOS F16 beta (which presumably would have been reset upon removal of battery)

Thanks for any help. I am about to throw this PC at the wall. I know it is time for a new PC given its age, but for the internet, media hub, and graphics it was all I needed really.

I have seen 4 other posts online with the EXACT same problem, but they never get a solution from anyone, so not sure how their issues resolved in the end.