Lights On, Nobody Home: Troubleshooting a Non-Starting Computer


I’ve encountered an issue where my computer shut down unexpectedly while I was viewing a video online. Although it powered off, some indicator lights remained illuminated. I attempted a hard reset by pressing and holding the power button, then waited a few minutes before trying to restart it. Upon doing so, the lights briefly flashed and the fans began to spin, but they ceased almost immediately, and the computer failed to boot up. I’m concerned that this could be related to the power supply unit (PSU) or the central processing unit (CPU), but I’m uncertain about how to diagnose or fix the problem. Your guidance on how to proceed with troubleshooting or recovery would be greatly valued.

Regrettably, I have a video clip that illustrates the issue but I’m unable to share it here.”


When your computer fails to boot, it can be a source of significant concern. The symptoms you’ve described suggest a few potential culprits, and there are several steps you can take to diagnose and possibly resolve the issue.

The power supply unit (PSU) is often a common cause of the symptoms you’re experiencing. When the lights flash and the fans spin briefly before shutting down, it could indicate a PSU unable to provide consistent power. To test this:

  • Ensure all cables are securely connected, both inside and outside the case.
  • If possible, test with another compatible PSU.

Step 2: Internal Connections and Components

Loose or damaged components can also prevent a computer from booting. Carefully inspect and reseat the following:

  • RAM sticks
  • Graphics card
  • All cable connections

Step 3: Motherboard and CPU

If the PSU and internal connections are not at fault, the issue may lie with the motherboard or CPU. This is more challenging to diagnose without spare parts to swap and test. However, you can:

  • Check for any visible damage on the motherboard.
  • Listen for beep codes when attempting to boot, which can indicate specific hardware issues.

Step 4: Minimal Boot

Try booting with the bare minimum hardware connected:

  • Remove all peripherals except for the monitor, keyboard, and mouse.
  • Disconnect any additional hardware like secondary drives or extra RAM modules.

Step 5: Clear CMOS

Resetting the BIOS can sometimes resolve boot issues:

  • Locate the CMOS battery on the motherboard.
  • Remove it for a few minutes, then reinsert it to reset the BIOS settings.

Step 6: Seek Professional Help

If none of the above steps work, it may be time to consult with a professional technician. They can provide a more thorough diagnosis and suggest repairs or replacements if necessary.

Remember, while it’s possible that the PSU or CPU could be the issue, it’s essential to methodically troubleshoot each component to avoid unnecessary replacements. Good luck with your troubleshooting efforts!

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