hp z620 wont boot after hard power down

[Calaudude]

Hello, my  11y daughter did a hard power down to  "relax" me and stop working on PC

well its 35C dgreesees outside

so first she is removing the ventilators which blow me some air to the face

then she removed my cold water from the table

then she powered down the pc

after I did manual power on again I saw bios but windows didnt boot up (somewhere after login in went black)

after 2nd power up  I see the power led going off after 3s and the disk drive activity stay on permanent green 

I am pretty much puzzeled what can I do now?

[Calaudude]

update I disconnected everything  drives and cables and still same green light and otherwise no function

did exchance it then with my spare HP Z620 

any clue how to revive the HP Z620 ?

[SDH]

I'm assuming you reset your CMOS on the original motherboard.

Try taking the boot drive from your working spare and try it in your non-working one.    The system install may have gotten corrupted...

[SDH]

Regarding reset of CMOS to defaults....  

There is the short way... push the button for 5 seconds.

There is the long way, and the only way I do it because corruption of CMOS can get stuck and not correct with way 1.  Unplug the power from the workstation.  Unplug everything else, and I mean everything.  Power can feed into the motherboard from unexpected sources such as ethernet cable, video cables, etc.  I put them back in where they came from so take some notes.  Certain USB-connected devices will have settings tagged to a specific USB port on install.

Now remove the motherboard battery... they can be a hassle to get out and a bamboo skewer stick can help plus keep you from shorting something out.  I put a piece of tape on the exposed metal of the battery, long enough to prevent it from flying out of position and shorting out on metal inside the case.  Now press and hold the power button in for 15 seconds to discharge capacitors.  Press and hold the CMOS button for 15 seconds.  Repeat these steps 3 times.  Reverse the order to gett all together again.  Plug in power to the workstation last.

This might be enough to limp back to function.

[Calaudude]

I will try these steps when I have some time

now  I keep my spare Z620 which is working fine