Windows 7 / Getting Started

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How to Create and Use a Virtual Hard Disk

Virtual hard disks (VHDs) are a file type that acts like a hard disk. In previous versions of Windows, VHDs were used by virtual machines, such as those created by Microsoft Virtual Server 2005 or Microsoft Virtual PC. Additionally, Complete PC Backup in Windows Vista created a copy of the computer's hard disk as a VHD disk image.

Beginning with Windows 7, you can now mount VHDs exactly like a physical disk. By mounting a VHD, you can easily copy files to and from the virtual disk. Additionally, Windows 7 can be configured to boot from a VHD.

You can create a VHD from either the Disk Management snap-in or the command line. After you create the VHD, you must attach it and then format it before you can use it, just like a physical partition.

From the Disk Management console, following these steps:

1. Right-click Disk Management and then click Create VHD. Follow the prompts that appear.
2. Right-click the new disk and then click Initialize Disk. Click OK.
3. Right-click the new disk and then click New Simple Volume (or select a different volume type, if available). Follow the prompts that appear.

The new virtual disk is ready to be used, just like any other disk.

From the DiskPart command-line tool at an elevated command prompt, run the create vdisk command and specify the file (to name the file) and maximum (to set the maximum size in megabytes) parameters. The following code demonstrates how to create a VHD file at C:\vdisks\disk1.vdh with a maximum file size of 16 GB (or 16,000 MB).

DiskPart

  Microsoft DiskPart version 6.1.7100
  Copyright (C) 1999-2008 Microsoft Corporation.
  On computer: WIN7

DISKPART> create vdisk file="C:\vdisks\disk1.vhd" maximum=16000

Volume ###	Ltr	Label	Fs	Type	Size	Status	Info
Volume 0	F	New Volume	NTFS	Simple	20 GB	Healthy
Volume 1	E	New Volume	NTFS	Simple	40 GB	Healthy
Volume 2	R			DVD-ROM	0 GB	No Media
Volume 3	C		NTFS	Partition	75 GB	Healthy	System
Volume 4	D	New Volume	NTFS	Partition	52 GB	Healthy

DISKPART> select volume 0

  Volume 0 is the selected volume.

DISKPART> delete volume

  DiskPart successfully deleted the volume.

For additional options, run the command help create vdisk at the DiskPart command prompt.

After you create a VHD, you must attach it, create a partition, assign it a drive letter, and format it before it can be used. The following script (which must be run within a DiskPart session) demonstrates how to do this.

create vdisk file="C:\vdisks\disk1.vhd" maximum=16000
attach vdisk
create partition primary
assign letter=g
format