Windows won't start: how to fix boot problems step by step

Quick answer: what to try first when Windows will not start

1. Unplug everything: flash drives, external drives, printers, memory cards and chargers for phones. A device left connected can confuse startup.
2. Switch the laptop off by holding the power button, wait a minute, then turn it on again.
3. If it shows Automatic Repair or Recovery, choose Advanced options and try Startup Repair.
4. If that fails, try Safe Mode and System Restore or Uninstall Updates.
5. If nothing works, protect your files before trying a reset, or take the laptop to a technician.

Do these in this order. Each step is gentler on your files than the next.

Why does Windows fail to start? The common causes

• A failed or interrupted update. A power cut or forced shutdown during an update is a classic cause.
• Corrupted system files after a sudden shutdown, a virus or a flat battery.
• A damaged boot configuration. The small part of the drive that tells the laptop where Windows is can break.
• A bad driver or software install, especially graphics, antivirus or security tools.
• Disk errors or a failing drive.
• Hardware faults, such as loose or faulty memory, a loose drive connection, or a failing board.

Software causes can be fixed. Disk and hardware causes need protection of your files first, and sometimes a repair or a replacement part.

Step 1: read what the screen is telling you

Do not skip this. Write the message down or photograph it with your phone. Common ones:

• Preparing Automatic Repair or Diagnosing your PC. Windows has detected failed starts and is trying to fix them. Let it finish, which can take a while.
• Your PC did not start correctly. The recovery menu is about to give you options.
• Operating system not found, No bootable device, or Boot device not found. The laptop cannot see Windows on the drive. This could mean a damaged boot setup, a wrong boot order, or a drive that is not detected.
• Reboot and select proper boot device. The same idea. Check for a USB drive left in, and check the boot order.
• INACCESSIBLE_BOOT_DEVICE. Windows cannot read the drive during start. It can follow an update, a drive setting change or a drive fault.
• A blue screen with a stop code. Write the code down; it points to the cause.
• Stuck on the manufacturer logo or a spinning circle for a very long time. Often a failed update or drive fault.
• A black screen with a blinking cursor. Often a boot record or drive problem.
• A BitLocker recovery key screen. The laptop encrypts the drive and wants the key, often after a hardware or setting change. Find the key in your Microsoft account on another device, or from your organisation.

Step 2: get into the Windows Recovery Environment

The Windows Recovery Environment holds the repair tools. You can reach it in three ways:

1. Let it appear on its own. After two or three failed starts, Windows usually shows the recovery screen by itself.
2. Force it. Turn the laptop on, and as soon as the Windows logo or spinning dots appear, hold the power button until it switches off. Repeat this about three times, and on the next start choose See advanced repair options. Do this only when you have no other choice, because forced shutdowns can add file damage.
3. Use installation media. On another working computer, make a Windows USB installer using Microsoft's official download page. Start the broken laptop from it (you may need to press a boot-menu key such as F12, F9 or Esc at power-on, which differs between makers), choose your language, then Repair your computer.

When you see the blue Choose an option screen, click Troubleshoot, then Advanced options. You will see the tools used in the next steps.

Step 3: run Startup Repair, System Restore and Uninstall Updates

1. In Advanced options, choose Startup Repair. Pick your account and enter the password if asked. Wait for it to complete. It may say it could not repair your PC, which is a normal outcome.
2. If that fails, return to Advanced options and choose System Restore, if available. It rolls Windows back to an earlier restore point without touching your documents. It only works if restore points were created before the problem.
3. If the trouble started after an update, choose Uninstall Updates, then try removing the latest quality update first, and then the latest feature update if needed.

After each step, restart and check if Windows starts. Do not run all the tools in a row without testing; you will not know what worked.

Step 4: try Safe Mode

Safe Mode starts Windows with only basic drivers. If it works, a driver or program is the culprit.

1. In Advanced options choose Startup Settings, then Restart.
2. Press 4 or F4 for Safe Mode, or 5 or F5 for Safe Mode with Networking.

Once in Safe Mode:

• Uninstall the last program or driver you added: Settings, Apps. For a graphics driver, use Device Manager, Display adapters, and uninstall the device.
• Run a virus scan with your security software.
• Open Settings, Windows Update and see if updates failed. Use View update history, Uninstall updates, for the latest one.
• Copy important files to an external drive while you have access.

Restart normally afterwards. If the laptop only starts in Safe Mode, the problem is still in a driver or startup program, so remove or disable the recent ones.

Step 5: check the disk and repair system files

In Advanced options, choose Command Prompt. In this environment your Windows drive often has a different letter from C. To find it, type diskpart, then list volume, look for the volume whose size matches your main drive, then type exit.

Assuming it is C, run:

1. chkdsk C: /r to scan for disk errors. It can take a long time on a large drive. If it reports a lot of bad sectors or runs painfully slow, the drive may be failing; stop there and protect your files.
2. sfc /scannow /offbootdir=C:\ /offwindir=C:\Windows to repair system files.
3. bootrec /scanos to see whether Windows is found, then bootrec /rebuildbcd to rebuild the boot list.

If bootrec reports Access denied, or you are unsure about the commands, stop. The deeper boot repair for modern laptops involves boot partitions and carries a risk of making things worse. This is the point where a technician is the safer choice.

Check the BIOS. Switch on and press the setup key (often F2, Del, F10 or Esc). Does the drive appear in the storage or boot list? Is the date correct? A drive that does not show up may be a loose connection or a failed drive. A wrong date and time every start can mean a flat clock battery, which can upset boot settings. Do not change settings you do not understand.

Protect your files before you reset or reinstall

A reset or fresh install is the last software step, and it can erase files. Copy what matters first.

1. In the recovery Command Prompt, type notepad and press Enter.
2. In Notepad, click File, then Open. Change the file type to All Files. Click This PC, and you can browse the drives and folders like File Explorer.
3. Plug in a USB drive or an external drive, then copy files from Users, then your name, then Documents, Desktop, Pictures and Downloads. Right-click a folder and choose Copy, then paste to the external drive.

If that is too awkward, or the drive is not visible, a technician can connect the drive to another computer or an adapter and copy the files without writing to it. Your files are worth more than the Windows installation.

When your files are safe, use Reset this PC from Troubleshoot or reinstall Windows from installation media.

When it is hardware, and when to get help

Suspect hardware, and stop software attempts, when:

• The drive does not appear in BIOS, or appears with the wrong size.
• You hear clicking, grinding or repeated spin-up noises.
• The laptop restarts or freezes within seconds, even in recovery or from a USB installer.
• Startup problems appear with beeps, flashing lights, a screen that stays black, or random crashes.
• The laptop was dropped, wet, or very hot before the problem.

A technician can test the drive, memory and board, recover your files, then repair or replace the faulty part and reinstall Windows. Ask for your files to be recovered first, and for a clear explanation of what failed.

Frequently asked questions

Written by the ICT AccessPoint team

We repair laptops and build websites and business systems. Have a question this guide did not answer? Message us.

This guide is general advice. Every device and business is different, so if you are unsure, ask a technician before you act.