Fix: C Drive Filling Up by itself on Windows 10/11

When your C drive starts auto-filling unexpectedly, you may notice a sudden and significant reduction in available storage space. This often leads to low disk space warnings and performance issues. If not addressed promptly, this issue can escalate into potential system crashes or even lost data. This problem typically occurs when the operating system or certain applications generate large amounts of temporary files, system logs, or even due to malware.

The primary cause of this issue is often related to automatic updates, system restore points, or leftover files from software updates, especially in systems where disk space management isn’t optimized.

1. Disable Hibernation

Hibernation is a feature that saves your current session to your hard disk, allowing your computer to power off without losing your current progress. Over time, the hibernation file can become quite large. To delete it, you’ll need to disable hibernation:

1. Press the Windows key, type cmd, then right-click and choose Run as administrator.

   

2. In the Command Prompt, type powercfg.exe -h off and hit Enter.
3. This command will disable hibernation and delete the hiberfil.sys file.
4. Check if the issue is resolved.

2. Clear Temporary Folder

Windows stores temporary files in a system directory, which can grow significantly over time, potentially causing your system drive to appear as though it’s filling itself.

1. Press Win key + R to open the Run dialog.
2. Type %temp% and hit Enter.

   

3. In the Temp folder, press CTRL + A to select all files, then press SHIFT + DEL to delete them permanently.

   

Learn more about temporary files and if it’s safe to delete them.

3. Check System Restore Points

System restore points, which are snapshots of your system taken during updates or software installations, can gradually accumulate and occupy a large portion of your disk.

By regularly checking and managing these restore points, you can free up a significant amount of storage space.

1. Open the Start Menu, type System Restore, and select it.

   

2. Select C drive, then click ‘Configure‘.

   

3. Check the maximum storage size for restore points.
4. If Current usage is high, delete old restore points.

   

5. Adjust the Max Usage slider to set the storage space for restore points.

4. Run Malware Scans

Malware can silently consume large amounts of space by creating hidden files or manipulating your system. Running a thorough malware scan can identify and eliminate malicious software responsible for this behavior.

1. Press Win key + I to open the Settings app.
2. Go to Privacy and Security > Windows Security > Virus and Threat Protection.

   

3. In the Windows Security window, click Scan options.

   

4. Select Full scan and click Scan now.

   

5. Wait for the scan to complete.

Consider using a reputable third-party antivirus program, such as Malwarebytes, for additional scan options.

5. Use TreeSize

The TreeSize utility provides a detailed visual breakdown of your disk space usage, revealing exactly which folders and files are taking up the most room. By using TreeSize, you can quickly identify large or unnecessary files that might be hidden deep within your directories.

1. Follow the instructions to install the application.
2. Open TreeSize from the Start Menu and run it as an administrator.

   

3. Select the C drive for analysis.

   

4. Allow the scan to complete.

   

5. Use the ‘Size‘ column to identify and delete the largest files.

6. Clean Install Windows

When other methods fail, a clean installation of Windows might be your last resort. This will format your C drive, eradicating any issues that cause it to fill up spontaneously.

Ensure you back up any important data before proceeding, as formatting will erase your data irrevocably.

You can follow our detailed guide here on performing a clean Windows installation step by step.

The solutions provided herein should assist in restoring your system storage and preventing your C drive from self-filling. If the issue persists, we recommend contacting the Windows support team for further assistance.