Windows won’t start

CHKDSK runs every time you start the PC and never finishes

Windows runs a disk check (CHKDSK) automatically on every boot, but it either restarts before finishing, gets stuck at a percentage, or loops back to running again on the next startup without resolving anything.

Difficulty
Intermediate
Time
1–6 hours
DIY cost
$0–$70
Pro cost
$100–$300

Symptoms

  • Blue-ish text screen showing CHKDSK scanning a percentage on every boot
  • Percentage stalls or the PC restarts before completion
  • Same scan restarts on the next boot attempt
  • May follow an improper shutdown, power outage, or detected disk errors

Likely causes

  • CommonDrive has significant bad sectors or file system damageSevere corruption can make CHKDSK's repair process itself unstable or very slow.
  • CommonDirty bit repeatedly being set due to improper shutdownsIf the PC keeps shutting down incorrectly, Windows will keep flagging the drive for a check.
  • PossibleFailing drive hardwareA physically failing drive can cause CHKDSK to hang or restart the system during the scan.
  • PossibleInsufficient time given before assuming it's stuckLarge drives with many files can take several hours for a full check, especially mechanical drives.
  • Less commonCorrupted CHKDSK log or system file interfering with completion trackingRarely, a logging issue can make CHKDSK appear to loop even after completing.

What to do

  1. Let a single CHKDSK pass run for at least 2–4 hours before assuming it's stuck, especially on large or mechanical drives.
  2. If it does appear frozen (no percentage movement for over an hour) force a restart and let it try again once.
  3. If it loops a second time, boot into Windows Recovery Environment via installation USB and run 'chkdsk C: /r' manually from Command Prompt, which gives more control and visible output than the automatic version.
  4. Consider running 'chkdsk C: /scan' first, which is faster and only scans without immediately trying to fix, to gauge the extent of damage.
  5. If scan results show extensive bad sectors, back up all recoverable data immediately, since the drive is likely failing.
  6. If the check does eventually complete successfully, monitor whether it's triggered again on the next few boots; if it keeps recurring, the drive should be considered unreliable.
  7. Once you have any usable data backed up, plan to replace a drive that repeatedly requires CHKDSK or shows significant bad sector counts.

Tools and parts

  • Bootable Windows installation USB drive
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When to call a pro

If CHKDSK reports heavy bad-sector damage or keeps recurring, treat the drive as failing; a data recovery professional can help retrieve files before you replace it.

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.