Windows won’t start

Black screen with only a blinking cursor in the top-left corner

Before Windows even starts loading, the screen shows nothing but a small blinking text cursor in the top-left corner and never progresses further, which points to a problem happening before the operating system loads at all.

Difficulty
Intermediate
Time
20–60 minutes
DIY cost
$0–$60
Pro cost
$100–$220

Symptoms

  • Blinking underscore or block cursor appears alone in the top-left of a black screen
  • No BIOS logo, Windows logo, or any other text appears
  • Happens consistently on every power-on
  • PC otherwise seems to power on normally with fans running

Likely causes

  • CommonNo bootable drive detected by the firmwareThis specific blank-screen-with-cursor pattern classically means the BIOS/UEFI found nothing to boot from.
  • CommonCorrupted or missing Master Boot Record (MBR) / boot sectorDamage to the very first part of the drive that the firmware reads can cause exactly this symptom.
  • PossibleDrive not properly connectedA loose cable prevents the firmware from finding a boot target.
  • PossibleBoot order pointing at an empty removable deviceIf the first boot device in order is empty, this blank cursor screen can appear.
  • PossibleDrive failureA dead drive presents the same way as one that's simply disconnected.

What to do

  1. Check that no empty USB drive, memory card, or disc is inserted, and remove any that are, then restart.
  2. Enter BIOS/UEFI setup (tap Del, F2, or Esc repeatedly at power-on) and verify the internal drive is detected in storage information.
  3. If detected, check and correct the boot order to prioritize the internal drive.
  4. For desktops, power off, unplug, and reseat the drive's power and data cables if it's not detected.
  5. If detected but still stuck at this screen, boot from a Windows installation USB and use 'bootrec /fixmbr' and 'bootrec /fixboot' from Command Prompt to repair the boot sector.
  6. If the drive isn't detected in BIOS at all after reseating cables, it likely has failed and needs professional testing.
  7. Back up any accessible data as a priority if there's any chance the drive is failing rather than simply misconfigured.

Tools and parts

  • Bootable Windows installation USB drive
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When to call a pro

If BIOS doesn't detect the drive after checking cables, or bootrec commands can't repair the boot sector, a data recovery professional should look at the drive before further attempts.

Safety

Generally low risk

Generally low risk for a careful person. Stop if anything looks different from what this guide describes.

Related guides

Operator provides AI-generated troubleshooting information. It can be wrong. For safety-critical, electrical, gas, structural, medical, automotive safety, or other high-risk problems, consult a qualified professional.