• Windows
  • Backups

WindowsImageBackup is a full copy of the drive, kept forever

A system image is the size of everything in use, stored as virtual disks. How to find old sets, remove them safely and keep only what helps.

5 min read

A system image is not a backup of your documents. It is a copy of everything in use on the drive at that moment, stored as virtual disk files, and it is the largest single thing most people ever put on an external drive.

What the folder contains

ItemWhat it is
WindowsImageBackup\<PC name>\Backup <date>One complete image set
*.vhdx files inside a setThe drive contents, one file per volume imaged
Catalog and MediaIdWhat the restore tool reads to find a set
SPPMetadataCacheMetadata for the set, small

The rule that surprises people: a set is the size of the used space on the volumes it covers, not the size of the drive. Imaging a 500 GB SSD with 180 GB in use produces roughly 180 GB of image, less whatever compression achieves.

Finding what is there

# Every image set on a drive, newest last
Get-ChildItem 'E:\WindowsImageBackup' -Directory -Recurse -Depth 1 -EA SilentlyContinue |
  ForEach-Object {
    $s = (Get-ChildItem $_.FullName -Recurse -Force -File -EA SilentlyContinue |
          Measure-Object Length -Sum).Sum
    [PSCustomObject]@{ GB = [math]::Round($s/1GB,2); Modified = $_.LastWriteTime; Path = $_.FullName }
  } | Sort-Object Modified

Removing old sets

  1. Backup and Restore (Windows 7) in Control Panel, then Manage space, then View backups. This removes sets through the tool that made them and keeps the catalogue honest.
  2. Delete a whole dated set folder if the tool will not run, for example when the machine that made it is gone. Delete the entire Backup <date> folder, never individual files inside one.
  3. Never delete the Catalog folder while keeping the sets, which leaves images that the restore tool cannot see.

An image only ever restores as a whole volume, so a set you cannot restore from is worth nothing. That is the reason to be strict with these: keep the most recent one and perhaps one older, and delete the rest deliberately.

Whether you need one at all

You want to recoverThe right tool
A document from last TuesdayFile History
A file you overwrote an hour agoPrevious Versions, from a shadow copy
The whole machine after a disk failureA system image
The machine exactly as it was before an updateA restore point

Most people want the first two and have the third, which is why backup drives fill. File History covers versions of your own files, and shadow copies cover the short term on the internal drive.

Common questions

Can I delete the WindowsImageBackup folder?

Yes, if you do not intend to restore from it. Remove whole dated sets rather than individual files inside one, and prefer Backup and Restore, Manage space, so the catalogue stays consistent.

How big is a Windows system image?

Roughly the used space on the volumes it covers, not the size of the drive. A 500 GB SSD with 180 GB in use produces an image of about that, less any compression.

Why can I not open the files in a system image?

Because the contents are stored as virtual disk files. They are readable by the restore tool, and can be mounted read only by Disk Management, but they are not a folder of your documents.

How many system images should I keep?

Usually one or two. Each is a full copy, so a third old set is normally worth less than the space it costs on the backup drive.

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