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Why did my drive gain 800 GB overnight?

NM Master 0 Reputation points
2025-10-25T22:18:27.53+00:00

I came to my computer today, and I saw my desktop with storage full notifications. I checked file explorer and disk cleanup, and file explorer said it was full, and disk cleanup did not say there was anything big to cleanup. I uninstalled a few apps thinking it was malware, so I could scan my device. I installed wiztree and it said I had a log file from powertoys light switch which contained over 700 GB of data. It also said I had a second one which contained over 75 GB of data. I had turned off light switch the day before because of the bug that I found while trying to fix it auto switching to light mode. I turned it off from the official powertoys settings app. Why did this bug happen and will it happen again? Thank you in advance. EDIT: It also had a few powertoys error, something about it running out of disk space and having to stop. I also had to use file locksmith to unlock the file because light switch was still using it. Please let me know if this will cause problems.

Windows for home | Windows 11 | Files, folders, and storage
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  1. Hendrix-V 4,985 Reputation points Microsoft External Staff Moderator
    2025-10-26T04:03:54.65+00:00

    Hi NM Master,

    Thank you for reaching out to the Microsoft Q&A Forum! I completely understand how concerning it is when disk space disappears without warning, and I’m here to help you get clarity and peace of mind.

    Based on your description, Light Switch continued writing logs excessively even after being disabled. This occurred because the background service remained active, repeatedly logging theme changes and errors. As a result, files as large as 700 GB and 75 GB were created. While these logs did not harm the system, they consumed significant disk space. Using File Locksmith to unlock and manage them was the correct approach.Here are the steps you can follw to fix it now:

    1. Update PowerToys via Settings or run this command in Command Prompt (as Administrator): winget upgrade Microsoft.PowerToys
    2. Turn off Light Switch in PowerToys settings.
    3. Stop the LightSwitch service (exit PowerToys or end the process in Task Manager).
    4. Delete the oversized log files from: %LOCALAPPDATA%\PowerToys\LightSwitchService\Logs

    You did everything right by investigating, uninstalling suspicious apps, and using WizTree to identify the culprit. Once you update PowerToys and clear those logs, your system should be back to normal.

    I look forward to receiving your update. Let me know if you need further assistance, feel free to ask me by clicking "Add Comment". Thanks for your effort.

    If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have additional questions about this answer, please click "Comment".

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