A virtual hard disk is a portable encrypted container, a backup target or a test sandbox. Mount it with Mount-DiskImage, give it a letter and make it attach itself at every logon.
Create the file with **New-VHD** or **diskpart**, attach it with **Mount-DiskImage**, partition it once, then schedule **Mount-DiskImage** at logon so the letter appears before you open Explorer.
**New-VHD** makes a dynamically expanding file, so a 200 GB disk occupies only what it stores. Fixed sizing is faster but reserves the full size on day one.
New-Item -ItemType Directory D:\Vault -Force | Out-Null
New-VHD -Path D:\Vault\data.vhdx -SizeBytes 200GB -Dynamic
Get-VHD -Path D:\Vault\data.vhdx | Select-Object Path,Size,FileSize,Attached**Mount-DiskImage** attaches the file as a real disk. The disk is offline until it is brought online, and its number is what every later diskpart command needs.
Mount-DiskImage -ImagePath D:\Vault\data.vhdx
Get-DiskImage -ImagePath D:\Vault\data.vhdx | Get-Disk | Select-Object Number,OperationalStatus,PartitionStyle
Get-Disk | Where-Object Location -like '*data.vhdx*' | Select-Object Number,FriendlyNameThis is the same initialisation a physical drive needs. After the format, Windows remembers the volume and the letter is reused on every attach.
Initialize-Disk -Number 3 -PartitionStyle GPT
New-Partition -DiskNumber 3 -UseMaximumSize -AssignDriveLetter | Format-Volume -FileSystem NTFS -NewFileSystemLabel Vault -Confirm:$false
Get-Volume -FileSystemLabel Vault | Select-Object DriveLetter,Size,SizeRemainingA mounted VHDX disappears at reboot. A logon task that runs **Mount-DiskImage** restores it silently, and the volume keeps the letter it was given.
$a = New-ScheduledTaskAction -Execute 'powershell.exe' -Argument '-NoProfile -WindowStyle Hidden -Command "Mount-DiskImage -ImagePath D:\Vault\data.vhdx -NoDriveLetter:$false"'
$t = New-ScheduledTaskTrigger -AtLogOn
Register-ScheduledTask -TaskName 'Mount Vault VHDX' -Action $a -Trigger $t -RunLevel Highest -User $env:USERNAME
Get-ScheduledTask -TaskName 'Mount Vault VHDX' | Select-Object TaskName,StateReboot, sign in, then read the volume and the image state. **Attached** must be true and the letter must be the one from the format step.
Get-DiskImage -ImagePath D:\Vault\data.vhdx | Select-Object Attached,DevicePath
Get-Volume | Where-Object FileSystemLabel -eq 'Vault' | Select-Object DriveLetter,HealthStatus
Test-Path V:\**Dismount-DiskImage** flushes the volume and closes the file, which is what makes the container safe to copy. Unplugging the drive it sits on without this step is how VHDX files get corrupted.
Dismount-DiskImage -ImagePath D:\Vault\data.vhdx
Get-DiskImage -ImagePath D:\Vault\data.vhdx | Select-Object Attached
Get-Item D:\Vault\data.vhdx | Select-Object Name,Length,LastWriteTimeBring it online with Set-Disk -Number 3 -IsOffline $false, then check OperationalStatus before partitioning.
Another volume grabbed the letter first. Assign a letter at the high end with Set-Partition -DriveLetter, or set it in the disk's mount manager entry.
The task must run in the user session with highest privileges. Check LastTaskResult with Get-ScheduledTaskInfo and the task history for an access-denied entry.
A file or a program still uses the volume. Close it, or run Get-Process and stop the handle holder before retrying.
No. Booting from a VHD makes the container the system disk and needs a boot entry. Here the file is just a data volume that appears as a normal drive.
Yes, either with a drive encryption tool on the host volume that holds the file, or by enabling encryption inside the mounted volume itself.
Up to 64 TB on NTFS, but keep the dynamic file well below the free space of the host drive so it never fails to expand.
Unregister the logon task with Unregister-ScheduledTask -TaskName 'Mount Vault VHDX' -Confirm:$false, dismount the image, then delete the VHDX file. Any data stored on the volume goes with it.
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