Windows won’t start

BIOS settings keep resetting, causing repeated boot failures

BIOS/UEFI settings like boot order, date/time, and enabled features keep reverting to defaults between power-offs, which in turn causes Windows to sometimes fail to boot until settings are manually corrected again.

Difficulty
Moderate
Time
20–45 minutes
DIY cost
$5–$15
Pro cost
$60–$150

Symptoms

  • System clock resets to a wrong date/time after being unplugged or losing power
  • Boot order or other BIOS settings need to be reconfigured repeatedly
  • Sometimes Windows fails to boot until BIOS settings are fixed again
  • More noticeable after the PC has been unplugged or the battery has drained

Likely causes

  • CommonDead or dying CMOS batteryThis small battery maintains BIOS settings when the PC is unplugged; once it dies, settings reset every time power is fully removed.
  • PossibleBattery connector loose or corrodedA poor connection can cause intermittent rather than constant resets.
  • Less commonMotherboard fault affecting settings storageIn rare cases the issue isn't the battery itself but the circuitry that reads it.

What to do

  1. Note whether the clock/date resets specifically after the PC has been unplugged from power for a while, which strongly points to the CMOS battery.
  2. For desktops, power off and unplug the PC, then open the case to locate the small round CMOS battery (usually a CR2032 coin cell) on the motherboard.
  3. Note its orientation, then gently remove it and replace it with a fresh identical battery, widely available and inexpensive.
  4. After replacing the battery, boot into BIOS/UEFI and reconfigure boot order, date/time, and any other settings you rely on, then save and exit.
  5. For laptops, the battery is usually harder to access and may require removing the back panel or keyboard; check your model's service manual or consider professional help.
  6. If replacing the battery doesn't stop the resets, check that the battery connector or socket looks clean and properly seated.
  7. If problems continue with a fresh battery properly seated, the motherboard's battery circuit may be at fault and needs professional diagnosis.

Tools and parts

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When to call a pro

If a fresh CMOS battery doesn't stop the settings from resetting, especially on a laptop, a technician can check the battery connector and motherboard circuitry.

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.