How can you fix boot errors when nothing gets displayed to your computer screen? There’s no details, there’s no error message, there’s no secret code or is there? It looks like you have a black screen in Windows and nothing is happening. I have written many articles on troubleshooting a black screen on startup but this article is about using a diagnostic post card to find the problem.
A small, inexpensive device sits in every PC repair technician’s toolbox, it’s a Power-On Self-Test (POST) code checker. POST is a quick set of diagnostic tests run by every computer during the first few seconds of booting. As the computer checks each component it needs to boot, it sends a special code that a POST code checker can print. By reading the code you can watch in real-time as your computer boots up–and see for yourself which hardware fails.
Fix Boot Errors By Understanding How Booting Works
Every Intel or AMD-based computer goes through the same boot-up cycle whether it runs Windows, Linux, or even Intel-based Mac OS X.
First, when you plug the computer into the wall, a tiny bit of electricity travels through the motherboard to the power switch on the front of the computer. Pressing that switch routes the electricity back to the computer’s motherboard, telling it to turn on completely.
The motherboard powers up the Computer Processing Unit (CPU). Stored directly on the motherboard is a special file which contains a program (called the BIOS, see how to access the BIOS); the motherboard uses the CPU to run this program.
The BIOS contains commands to identify and turn on the hardware in the computer, one piece of hardware at a time. Different BIOSes turn on the hardware in different order, but here is a common sequence of events stored in the BIOS program:
- Find the computer memory (RAM), do a quick test to see how much RAM is available, activate the RAM, and load the full BIOS into RAM.
- Find each video card and use basic VGA instructions to activate each video card so the user can see what is happening.
- Find any keyboards and activate them so the user can send instructions to the BIOS. (Some recent BIOSes also find mice.)
- Look for anything that can be used as a bootable drive: hard drives, CDROM/DVD drives, USB drives, firewire drives, and others.
- Using the boot order set in the BIOS configuration, check each drive until one is found that is marked bootable and contains bootable code in the first sector of the drive.
- Run the bootable code found. At this point, the BIOS is finished running and it hands over full control of the computer to the bootable code. If this bootable code is not found or is corrupt, this is when we need to repair the boot sector of the hard drive. This will allow us to boot the computer again.
As the BIOS starts each piece of hardware above, the hardware gets a chance to communicate with the BIOS. The messages can’t be complicated, but each device can tell the BIOS whether or not its ready to do its job. If an essential device isn’t ready–for example, RAM, video, or all bootable disk drives–then the BIOS stops running.
Buying a POST Code Reader to Fix Boot Errors
The best news about POST code readers is that they’re dirt cheap. A quick search of Amazon for “post code” in “Computers and Networking” shows Buy It Now prices ranging from $10.99 to $36.99. Check out the link below;
Warning: some scam sites will try to sell POST code readers for $80 or even $100; they also sell special software for dozens or hundreds of dollars, don’t buy any of it. You shouldn’t need to spend more than $20. I bought the reader pictured above for $14 on Amazon several years ago.
Buy a POST code reader that plugs into a PCI port and includes a 4-LCD display. Unless you know you can use it, avoid so-called laptop POST code readers, they require the laptop have a parallel port, which most laptops don’t these days. I suggest you spend a little extra for a POST code reader that includes an extension cable so you can read the code without sticking your head in the computer.
Fixing Boot Errors With Your POST Code Reader
When you encounter a problem and want to fix boot errors, turn off your computer, open its case, and insert the POST code reader into a free PCI slot. Power on your computer and watch the codes as they appear on the code reader. Write down the code that appears immediately before or during the boot error.
Go to another Internet-connected computer and search for that code and your motherboard type, remember POST codes come from the BIOS and the BIOS is unique to each motherboard.
For example, your post code reader says 2B when the computer stops booting. The computer runs Dell BIOS, so you search Google for dell bios post 2B. As of this writing, three of the top four results all point to a listing of Dell BIOS post codes, including an explanation that “2B” means “Video memory test failed.”
Use the information you get from the code description to attempt to fix boot errors. In the case of the above error, I would remove the graphics card from the computer, clean its connectors, reinsert it, and try booting again; if it still didn’t work, I’d replace the graphics card.
Each problem has its own solution, but you’ll be much closer to finding a way to fix boot errors once you have that essential POST code.
If you have any more computer tips on how to fix boot errors, please add a comment below.
Fix Boot Errors With Software
Using software to fix boot errors is Ok if it is not a hardware problem, although this software does repair the boot sector of a hard drive.. That is still repairing hidden files on your hard to get it working again.
You can easily buy a boot disc to repair your computer for you, however if you are going to fork out your money you might as well do it properly with something you can use for more than just one purpose. Before buying anything you should look at paying
This program will:
- Boot up computer even if it is infected with virus.
- Fast recovery from crashes such as bluescreen and blackscreen.
- Fix booting problems and random crash.
- Fix missing file crash such as “ntldr is missing”, “bootmgr is missing” etc.
- Repair partition table, corrupt registry, registry key value infected by virus, and crashed MBR even it is infected with virus.
- 1-click system file recovery.
- Rescue Windows 98/ME/2K/HOME/2003/XP/NT/Vista/7 Right up until 2024.
It will also recover files from a damaged hard drive, format, clean, clone and backup. Need I say more? This is what the computer techies use to fix your computer and charge you loads of cash per hour for their labor.
What a great article Dave! I learned a lot just by reading your article. I know there is a lot of variables of black screen. Mine happened after a MS update. I shut it down by mistake when it was still downloading the update. Upon shutdown a message appeared that said, “Windows will shut down your computer after updates are complete”, or something to that effect. I get the Dell splash screen, the Windows XP screen, and then the black screen. My cursor still works on the black screen and can move it anywhere on the screen. I am sad because I tried repairing a sector using check disk and tried using the last known good configuratiion but nothing worked. I can do a little using my installation disk but after it tries everything it still won’t boot. I think I may try the post code reader.
Les
If you can move the cursor around this must be the mouse. Does that sound right?
If it is then try hit CTRL ALT DEL to get the task manager to start, then press on new task and type in explorer.exe
Also does the computer start in safe mode?
Very interesting, I know more about how the computer starts now. But I almost only use laptops nowadays, what can I use for post code on a laptop?
You can do to recover data, fix all booting errors and scan the physical drive to recover all NTFS and FAT partition. Try Kernel for windows data recovery software are specifically designed to scan the entire hard drive thoroughly and achieve quick and proficient data recovery.