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Solved! Lost Disk Space After Defrag Windows 10/7 Computer!

Published/Updated on Thursday, February 27, 2025

M3 Software author Wilsey Young

Written by

Wilsey Young

English

The built-in defrag tool in Windows can optimize the hard drive performance by reorganizing fragmented files, which allows the system to read the file faster. In addition, defragmentation optimizes free space and improves system responsiveness.

Despite its benefits and convenience, defragmentation also brings problems. Some Windows 10/7 users come across the "lost disk space after defrag" issue and are desperate to know the causes. This post shows how to fix the "lost disk space after defrag" problem to restore the disk space.

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How to fix lost disk space after defrag on Windows 10/7?

The solutions introduced in this part also show the possible factors that may cause the "lost disk space after defrag" problem.

Run a virus scan through Settings on Windows 10/7

The malware or viruses in the system may be to blame for the "lost disk space after defrag" issue. You can follow the steps below to run a quick or deep virus scan:

  1. Click the gear icon in the Start menu or press the Windows+I keys to open Settings.
  2. Click Update & Security and choose Windows Security.
  3. Tap on "Virus & threat protection" on the right. 
    virus and threat protection in Settings on Windows
  4. Click the "Quick scan" button below to scan for the virus or malware. 
    virus scan settings on Windows
  5. Alternatively, click the "Scan options" to choose the deep scan on the new page.

Delete system restore points and adjust drive space used by VSS

Windows OS includes a system restore feature that relies on VSS (Volume Shadow Copy Service) to create restore points in case the system needs to be reverted to the previous state. Therefore, the existing system restore points and disk space used by VSS may be the culprit for the "lost disk space after defrag" issue.

Here's how to delete system restore points:

  1. Open Settings and tap on the System.
  2. Choose the About option on the left side panel, then click "System protection" on the right. 
    check system protection settings
  3. Choose the drive containing the system restore points and tap on the Configure button under the System Protection tab. 
    configure system restore settings
  4. Click the Delete button to delete all restore points. Click Apply and OK. 
    delete system restore points

Here's how to adjust the drive space used by VSS:

  1. Open the System Protection window again where you can configure restore settings.
  2. Move the slider of the Max Usage to adjust the maximum disk space used by VSS. 
    adjust max usage of VSS
  3. Click Apply and OK.

Delete shadow copies made by VSS

If you defragmented the disk that contains the system partition and found out the disk space got lost, directly deleting the volume shadow copies mistakenly created by VSS may resolve the "lost disk space after defrag" issue on Windows 10/7. Here's how to delete those shadow copies:

  1. Double-click This PC or My Computer on Desktop to open File Explorer.
  2. Right-click on the Local Disk C/C Drive and choose Properties.
  3. Tap on the Disk Cleanup button under the General tab.
  4. Click "Clean up system files." 
    clean up system files in Disk Cleanup
  5. Go to the "More Options" tab and click the "Clean up" button under the System Restore and Shadow Copies section. 
    clean up system restore and shadow copies

Format the disk

Formatting the disk is the last resort that can be used to resolve the "lost disk space after defrag" issue, as formatting erases all the data stored on the target disk. Of course, if you have had the disk divided into different partitions, it is suggested that you only format the partitions other than the system partition.

Backing up the data should precede formatting the disk. Regarding data backup, iBoysoft DiskGeeker for Windows is a professional and user-friendly tool that can help you easily clone all the data from one disk to another disk. The clone feature provided by this tool is to create an identical and uncompressed replica of the disk or partition, which means the partition structure and file systems will remain unchanged.

Here's how to clone the disk using iBoysoft DiskGeeker for Windows:

  1. Download, install, and launch iBoysoft DiskGeeker for Windows.
  2. Tap on the "Source disk" button to select the disk you want to clone. 
    iBoysoft DiskGeeker for Windows
  3. Click the "Target disk" button to choose where you would like to create a clone of the source disk. 
    iBoysoft DiskGeeker for Windows
  4. Check "Sector-level clone" if you need a 1:1 copy. Tick "Ignore bad sectors" if you don't want to be interrupted by bad sectors.
  5. Click the Start button and the tool will ask for your confirmation. 
    iBoysoft DiskGeeker for Windows
  6. Wait patiently.

 Tips: iBoysoft DiskGeeker for Windows also boasts the partition clone feature, which is useful when you plan to format one of the partitions in the disk.

Now you can move on to format the affected disk on Windows 10/7:

  1. Double-click This PC or My Computer to open File Explorer.
  2. Right-click on the affected disk and choose Format.
  3. Choose Quick Format and click the Start button.
    format flash drive in File Explorer

Conclusion

Suppose you hardly use the built-in tools or programs that rely on the VSS (Volume Shadow Copy Service), such as System Restore, and Windows File History. In that case, you can delete the system restore points, adjust the disk space usage, or disable the corresponding features, so the “lost disk space after defrag” issue may be fixed.

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