One day your computer might be working ok, and the next day you might see the "A disk read error occurred. Press Ctrl+Alt+Del to restart" message on the black screen, which cannot be solved with a simple restart. This error usually appears after restoring your system from an ISO image. Sometimes it also occurs when you are using a USB flash drive as a booting device, and sometimes it might appear from nowhere. In this article, we will explain the main reasons for the "A disk read error occurred" error and tell you how to fix it.
Main reasons for the "Disk read error occurred" error
The message you see on the screen partially explains what happened – the system could read your disk (and it means the disk used as a primary booting device). If would be great, if you know what actions or events happened before the error first appeared – it might help you to deduce the root of the problem and choose the most appropriate way to fix it. In case, you don’t know or don’t remember your last actions on the computer, here is a list of the most common reasons that cause the "A disk read error occurred" error:
- The corrupted file system on the disk (for example, as the result of unexpected improper computer shutdown after a blackout or system failure while creating partitions).
- Damaged or missing boot record and bootloader (may happen for the same reasons and sometimes after restoring OS from ISO image disk, usually created with third-party software).
- Wrong BIOS settings (after a reset or BIOS update).
- Hard-drive issues of physical nature (after a drop, natural wear down of components, unstable work, etc.). One dead giveaway – your computer may have been freezing during booting without for no apparent reasons.
- Hard-drive connection problems (for instance, you might have connected it loosely or incorrectly, or maybe contacts are damaged or your SATA cable).
- Not enough power after your power supply unit died: sometimes when a power supply unit malfunctions, your computer might be able to "work" but some components can spontaneously shut down (including your hard drive).
This information should give a foundation to make assumptions what caused the error we’re talking about. And what can you do in this particular scenario? Before you proceed, please make sure that your primary disk (the one used for booting by the system) is visible in BIOS (UEFI). If it is not, then it highly likely that something wrong with the disk connection. You should check cables and contacts on both ends (on your hard drive and your motherboard). The second reason could be more tragic – your storage device might be dead or have a serious hardware malfunction.
How to fix the "Disk read error occurred" error caused by the corrupted file system
The first and easiest thing to do would be to check the disk for errors. It requires you to boot your computer from a bootable USB flash drive (or CD/DVD) with diagnostics tools or simple bootable media with any versions of Windows (10/8.1/7). Here is a short example of this procedure:
- Insert your bootable USB flash drive into your computer (if you don’t have it, create a bootable media on another device – search our website for a guide that explains how to do that).
- Make that flash drive the primary booting device and start the system.
- After selecting the language, you need to click on "Repair your computer."
- If you have a bootable media with Windows 7, then click "Command Prompt." For Windows 8.1 and 10 users – "Troubleshoot" - "Command Prompt."
- In the Command Prompt window, you need to type two commands (clicking Enter after each one): diskpart and list volume.
- After executing the last command, you will see the letter of a system disk (it might be different from the standard C letter). You might see individual partitions with a bootloader without any letters. In order to check them as well, you need to assign letters to those partitions. In our scenario (see the screenshot above), we have to partitions without assigned letters, so it would be wise to check them – Volume 4 (Recovery) and Volume 7.
- The following command will help us to select the volume we need and assign any letter we want: select volume 7 and assign letter=Z (you can use any free letter here).
- Do the previous step for other volumes you want to check.
- When it is done, just type exit and hit Enter to close diskpart.
- Check all partitions one by one using this command: chkdsk C: /f /r (where C is the letter assigned to the disk, you need checking).
- Close Command Prompt, restart your computer and boot as usual from your hard-drive or SSD.
If you have found errors in important partitions during execution of the 10th step, it is highly likely that they are fixed now and your next system loading will be normal, without the "A Disk Read Error Occurred" error.
Corrupted bootloader Windows 10
If you suspect that the error we’re talking about was caused by the corrupted Windows bootloader, then you should check another article on our website where we explain how to fix Windows 10 bootloader.
A disk read error occurred as the result of wrong BIOS/UEFI settings
If you got this error after installing a BIOS update, resetting or altering some settings in BIOS, here is what you can try to do to fix it:
- If you have just installed an update or made some changes – reset all BIOS settings to defaults.
- After resetting, you need to check all settings carefully, especially hard disk modes (AHCI/IDE- if you don’t know which one to pick, try both variants – settings can be found in the SATA section).
- Check the boot order (boot sequence) in the Boot tab – the disk read error might be provoked by the wrong disk set as a primary booting device.
If none of these helps, and your problem was caused by the BIOS update, you should check whether it is possible to install the previous BIOS version on your motherboard. If it is, try doing so.
Hard drive connection issues
The "disk read error" may occur when your hard drive has some connection problems or SATA malfunctions. If you have been digging within your computer recently (or its case was open, and someone could accidentally touch cables), you should try to reconnect your HDD/SSD. Check both ends of the connecting cable. If it is possible, try a new one instead of the current cable.
- If you have installed a new (second) disk, try to disable it: if your computer boots properly without that disk, you should try to connect the disk again but to another SATA port.
- When your computer was not operational for a long time and just stood as it is without proper maintenance in conditions far from ideal, it is possible that oxidized contacts on cables or a disk may be the problem.
If none of these methods we detailed above was able to solve your problem, and you still see your disk on the list of connected devices, then you can try reinstalling your system (deleting all partitions in the process). If the "disk read error" occurs again shortly after the reinstall (or even right away) – it is likely that the cause of the error in the corrupted hard disk.