Question computer won't power on after using 24pin to 6+4pin cable!

[ba adbde]

Hi, my computer (HP Compact 8200 CMT) was working fine, then i decided to added a graphic card, but the graphic card that i bought needed a 6pin power supply and more Watts and i had one from an old PC, but the motherboard had a different PSU then what is common, instead of 24pin cable there was one with 6pins(2 yellow+2 black + 1 blue(-12V) + 1 purple (+12VSB)) and 4pin ( power_ok, power_on, and two more that had something to do with the PSU fan) and 4pin for the CPU and no SATA power supply instead they were supplied from the motherboard.
so i looked into the internet and found some videos on youtube and found about a cable that you can buy that convert 24pin To 6+4pin but for a different HP station (HP Z220 Z230 SFF) - it also converts +5vsb to +12vsb - after i got it i rearranged the pins of the 4pin cable and finally i got my computer to load after i click on F1 to skip the no PSU fan Dettected.
and then i tried to shutdown the computer and then at that moment when the fans and the green LED should stop, but it didn't the same thing when i try to put the PC to sleep, i tried to change the power management settings in the bios but no good, and then just on it's own every thing seemed like it was fixed on it's own.
so i played a game for a little bit and i set the Computer to sleep and went for about an hour and when i got back the PC was on! i got suspicious so i put it to sleep again and just as it shutdown it was up again on its own, i shutdown this time and again on its own it turns back on and i had to put the power down to get it to stay down. so after a minute or two of scratching my head thinking what the hell is going on i connected the power and tried to turn the PC on but that is not what happened!
when i click on the power button the power LED turns on but only for the brief moment that i'm clicking on the switch, but the computer doesn't turn on, so i checked the switch it was working, and returned to the first PSU but nothing changed, i also tried something i connected the PS_On with the ground to force the PSU to turn On and it did and stayed running, and then i clicked on the Power switch but still nothing happened and now i returned the PS_ON pin to It's normal state.
so here is what things look like, the power and computing LEDs are not on, but the green LED on the motherboard is always lit, and when i remove the CPU the power led is flashing red and a peep is heard.
so is there anything i could do to fix this motherboard? that is if it's really the motherboard that is faulty! is it possible that it's the CPU?

 

[Hamperking68]

Little bit confusing in the way I've read it so let me make sure I've heard you correctly.

Your GPU required a power power connector that your current power supply didn't have so you used as spare one which didn't fit into the Motherboard Main power connector?

Then the PC was behaving strangely like you've mention until which point it completely turned off. You've tried changing back to the old power supply however, the PC still won't boot.

If this is the case I would say the board is probably toast. But try reseating the memory and perhaps if you had another power supply you could try that too?

 

[ba adbde]

Little bit confusing in the way I've read it so let me make sure I've heard you correctly.

Your GPU required a power power connector that your current power supply didn't have so you used as spare one which didn't fit into the Motherboard Main power connector?

Then the PC was behaving strangely like you've mention until which point it completely turned off. You've tried changing back to the old power supply however, the PC still won't boot.

If this is the case I would say the board is probably toast. But try reseating the memory and perhaps if you had another power supply you could try that too?

yes and yes but it didn't just suddenly shutdown i was the one who turned the PC off, that is why i am suspecting the mechanism used by the motherboard to turn the PC on and off! (PS: this me an amateur who knows very little making a wild guess).

 

[ba adbde]

i just checked the amperage coming from the +12Vsb of that 24to6pin cable and found out that it was about 8 amps, that is way too high isn't it, could it be the reason the motherboard was damaged? if so then do you have any idea what part it was and if it's possible to fix?