Pc always turns on when powered

[Hekmeneer]

 

I have this computer that always turns on (and even tries to without power)

when it gets plugged in after having no power it goes on and of and then turns on to post (the machine still works)

i took out the motherboard and i saw no damage
i also tested it outside the case and it still did it

i also reseated the cpu and tried other ram.

the pc does not turn on without cmos battery (not even fans)

Its a HP wx4550 and it has no OS

things that are NOT the cause
wake on lan
wake on usb
other wake on settings
Power restore
The psu

The powerbutton (it also starts when i disconnect the fron panel io)
Cmos reset doesnt change anything
it is also not a bios timer

 

I do not need any advice on a new system i have enough could that could replace it, the only thing is that this one is better

 

How do i fix it, is it even possible to fix it?

Thanks in advance

[MrDrWho13]

Can you send it back and claim warranty?

[Hekmeneer]

1 minute ago, MrDrWho13 said:

Can you send it back and claim warranty?

Its 10 years old

[aisle9]

11 minutes ago, Hekmeneer said:

Its 10 years old

The ancient Optiplex 945s and 955s I spend a lot of time playing with tend to "turn themselves on" for a few seconds right after being connected to power. Think that might be what's going on here, or is it POSTing and staying on?

[Hekmeneer]

6 minutes ago, aisle9 said:

The ancient Optiplex 945s and 955s I spend a lot of time playing with tend to "turn themselves on" for a few seconds right after being connected to power. Think that might be what's going on here, or is it POSTing and staying on?

well,

if it has power it will turn on and post until i turn it off, but when it is off it wil turn on

but when i just plugged it in it wil turn on after 2 seconds and turn off directly and turn on again and then it will boot

[Hekmeneer]

i flashed the bios and that didnt work