The laptop running but black screen and lock A flashing.

[Twofi]

Dear all, 

I hope you having a good days!

My laptop is "EliteBook 8540w mobile workstation"
Windows 8.1 installed

It was running and I restart it then it start to show blue screen once the desktop loads right after the windows screen finish buffering, with error code 0xc000021a.

I could only format and install a new windows and i installed the same windows 8.1.

Then I installed the Nvidia driver and updated the Bios at the same time. Then it asked to restart to finish the setup, that when my laptop went black it runs like normal but with nothing on screen and lock A with continuous blinks sometimes both locks blink at the same time.

And even i leave it for hours nothing will show up. Even shutting it down with log press the power buttom will not work only when i remove the Ac cable and remove the battery.

I tried many things i will list them below:

- I removed the AC cable and battery with 60sec press on power.
- I removed Rams and hard disk.
- I removed and cleaned the whole motherboard, fan, CPU and GPU.
- I pressed the start buttom and while holding Window + B.
- I connected a monitor to it.
- I removed all accessed devices.

All things failed and now I am left with your

suggestions.

I appreciate your responses in advance.

[WAWood]

@Twofi 

The 21a stop code is due nearly always to corrupted Windows system files -- and while that can happen at random on a new PC, on a PC 3 years old or older, that is nearly always an indication of a failing drive.  And if that is the case with your PC, why did you presume that a fresh install of Windows would fix what amounts to a hardware issue?

If your PC is new enough to support UEFI, you can use these steps to test the hard drive: http://support.hp.com/us-en/document/c00439024

If not, to check the drive you have to follow these steps:
1) Press Esc key repeatedly, several times a second, while rebooting the laptop. Do NOT hold the key down, just press it over and over.
2) Eventually, you will see an HP Startup Menu -- that will look similar to the image below ...

3) press the Function key for testing the hard drive (usually F2) and let it run.

Please report back the test results.

[Twofi]

@wawood 

I assumed it is a windows failing since it access windows but sudden blue screen appears with that code. 

As for UEFI, that am not sure if my laptop support it. 

As for the steps I can't access any BIOS or checks total black when I start till I remove battery to shut it off. So I can't do those steps. 

The only thing I can see is a continuous blinking lockA on my laptop lights.

I appreciate your response 

[WAWood]

@Twofi 

I wish we could help you from here, but we can't. The problem is that we HERE, have no way of diagnosing or repairing hardware problems. And, with the PC not even starting, even HP Tech Support, who have the authority and tools to REMOTE into a PC across the Internet, can not access your PC.

Software failures invariably present with error messages of some kind on the screen, such as No Operating System or No Boot Device. In these cases, reinstalling the OS from media such as DVD or USB fixes the first; rebuilding the boot records using various utilities fixes the second. But any time a laptop simply refuses to turn on, that tend to indicate a serious hardware failure.

If your PC is still under the original one-year HP warranty, or if you have purchased an extended warranty from HP and this is still valid, then you should contact HP Customer Support to see about having it repaired or replaced under warranty.

If you live in the US or Canada, contact information is on this page: http://www8.hp.com/us/en/contact-hp/phone-assist.html#section1

If you live elsewhere, contact information is on this page: http://www8.hp.com/us/en/contact-hp/ww-contact-us.html

NOTE: After you get through, stay on the line until you are finally able to talk to some one -- it can take a while!
If you have trouble finding a phone number, then try: 1 (650) 857-1501.
Tech Support's number is 1 (800) 474-6836.

If your PC is no longer under warranty, you will have to contact an HP Repair or Service Center to see if they can examine the PC to determine the cause(s) of the problems, if it can be repaired, and an estimate of the repair costs.

If you live in the U.S., here is a link to the HP Service Repair Centers:
https://www.service-center-locator.com/hp-hewlett-packard/hp-hewlett-packard-service-center.htm

If you live outside the U.S., here is a link to HP Service Centers, by Country/Region: https://support.hp.com/in-en/service-center

Good Luck