PC won't start

Find where startup stops, then follow the guide for that message.

Starting a PC happens in stages: the firmware (BIOS/UEFI) checks the hardware, the Windows Boot Manager finds Windows, the Windows loader starts it, and then the Windows kernel takes over. Microsoft's startup troubleshooting begins by finding the stage where the PC gets stuck, because each stage has different causes.

Your files are usually still on the drive when Windows does not start. Do not reinstall Windows as the first step; work through the matching guide below first.

How to tell where startup stops

No picture at all, no maker logo, or only beeps or POST codes: the problem is in the hardware or firmware stage.
A firmware message such as "Boot Device Not Found" or "No bootable device": the firmware cannot find a drive to start from.
A black screen with "BOOTMGR is missing", or a blue Recovery screen with a code such as 0xc0000034: the boot manager or the boot configuration (BCD) is the problem.
The Windows logo appears and then a blue screen or a restart loop: Windows itself fails while starting.
Microsoft's quick hardware check: if the drive light does not flicker and NumLock does not respond, the PC is stuck before Windows. Disconnect external devices first.

No picture or no POST

The PC powers on but shows nothing, or the motherboard reports a code. These are hardware and firmware problems.

Graphics

GPU-BLACK-SCREEN

The PC turns on, fans spin and lights come on, but the monitor stays black or says "No signal". The monitor is not receiving a picture, either because the cable or input is wrong, or because the PC never finishes its…

high · Open step-by-step guide Motherboard

POST-CODE-55

On motherboards whose manual defines POST code 55 as memory not installed or not detected, startup has stopped during memory initialization. The number is a firmware diagnostic code, not a Windows error.

high · Open step-by-step guide

No boot device or boot manager

The firmware cannot find a drive to start from, or Windows' boot files and boot configuration are missing or damaged.

BIOS & startup

Boot Device Not Found

Before Windows starts, the PC shows "Boot Device Not Found", "No bootable device" or a similar firmware message. The message comes from the BIOS/UEFI, not from Windows: it did not find a drive it can start from.

critical · Open step-by-step guide Windows & BSOD

BOOTMGR-MISSING

Instead of starting Windows, the PC shows a black screen saying that BOOTMGR is missing and asking you to press Ctrl+Alt+Del to restart. BOOTMGR is the Windows Boot Manager on PCs that start in legacy BIOS mode.

critical · Open step-by-step guide Windows & BSOD

0xc0000034

Windows does not start and shows a blue Recovery screen with error code 0xc0000034. Microsoft's name for this code is STATUS_OBJECT_NAME_NOT_FOUND: the Windows Boot Manager looked for something it needs and could not…

critical · Open step-by-step guide

Windows starts and then crashes

Windows begins to load but stops with a blue screen or restarts. These usually need the Windows recovery environment.

Storage

First steps when the PC won't start

If your message is not listed yet, these steps from Microsoft's startup troubleshooting help in many cases. Do them in order.

Disconnect USB drives, docks and other external devices, then restart.
In the BIOS, check that the Windows drive is detected and first in the boot order, and undo any recent BIOS changes.
Create a Windows installation USB on another PC with Microsoft's media creation tool.
Start from the USB and choose Repair your computer > Troubleshoot > Advanced options > Startup Repair.
If that fails, use Uninstall Updates or System Restore from the same menu.
From the recovery Command Prompt, run chkdsk on the Windows partition and bootrec /scanos and bootrec /rebuildbcd.
Copy your files to another drive before resetting or reinstalling Windows.

Sources

Written and reviewed by Matyáš Rada.

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