How to restart, troubleshoot, repair, update and reinstall Windows. When Windows fails to start you may see a blue screen with an error, a continuous reboot loop, or nothing displayed on the screen. The computer may not start up after being shut down or after a restart.
The instructions in this article apply to Windows 10, Windows 8, and Windows 7 systems.
The reasons why Windows won't start
When a Windows laptop or desktop computer fails to boot, the cause could be a disconnected device, a missing file, a failed update, or a hardware failure.
What to do when Windows won't start
Follow the steps below in sequence to identify and fix the problem. In most cases, either of these solutions can get the system working again, but some problems may require replacing the failed hardware.
1. Restart your computer. Restarting restores access if the problem was simply an unusual glitch during the boot process.
2. On a desktop computer, check the connections. If you are using a keyboard or mouse with a cable, unplug and then plug them back in to verify that the devices are connected properly. A disconnected keyboard, for example, can cause the system to shut down during the boot process. Likewise, make sure the display cable is connected properly.
3. On a desktop computer, make sure the power light is on. If you can't see the light, the power supply may be bad. If absolutely nothing happens when you press the power button, the power supply may need to be replaced.
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4. Remove the battery. On a laptop with an easy-to-remove battery, unplug all power cords, then remove the battery. Then, with the battery disconnected, plug in the AC power cord and plug it into the laptop. Try starting your computer. If it boots up successfully, the problem is the laptop battery.
5. Let the updates complete. Windows often attempts to install system, application, and driver updates during the boot process. Especially if you have an older or slower system, these updates may take a long time to install. In some particularly problematic cases, you should leave your computer on overnight, then talk about it the next morning.
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6. Start Windows with the last working configuration. This option attempts to boot the system with any recent changes to the device, registry, and operating system restored to the settings that worked. This can allow the system to restore the system after a failed system or device driver update or an incorrectly configured registry entry. (When Windows doesn't boot twice in a row, the system should give you access to the Advanced Boot Options menu.)
If your system boots successfully with this method, you can immediately suspend the attempt to install system or device driver updates, as these updates could be the source of the problem. Check with Microsoft Support or the device manufacturer's site for recent news or information.
7. Run Windows Startup Repair. Startup Repair scans your system and attempts to repair missing or damaged system files. It may take more than a few minutes to complete and you may need to restart your computer. In some cases, you may need to run Startup Repair up to three times to fix startup problems.
8. Perform a system restore. Use a recent restore point to restore your system. A System Restore will restore the system, drivers, and registry to an earlier point in time.
9. Scan your computer for malware for several ways to remove malware. Some signs that your system may contain malware include virus warnings, warnings, or other unusual messages that appear at system startup.
10. Reset your PC. A reset will leave you with Windows and the apps originally installed on your system. Quite often, people initiate a Windows recovery when they are ready to get rid of the operating system, because they want to sell or give the computer to someone else.
A reset clears system customizations and changes, removes installed applications, and deletes data. However, it can be an effective way to get a problematic system back to a usable computer once again.
Make sure you've backed up your personal files elsewhere before performing a reset. A reset will erase your files.
11. Try an external hard drive. A failed or failing drive could prevent Windows from starting correctly. Hard drives with spinning parts often make screeching or noisy sounds when they fail, while solid state drives (SSDs) typically stop working silently.
If a drive has failed, you can install Windows on a new drive. If you haven't backed up your data elsewhere, you may be able to use data recovery software to attempt to recover files from the failed drive.
12. Perform a clean installation. If none of the above steps worked, you can try a clean install of Windows. This process will erase everything on the disk and replace it with a fresh Windows installation.