Simul-Post
The vhd Tool at MSDN by Chris Eck can crete large VHD’s via command line in seconds. Wow! this is better than chocolate ice cream and just short of Spumoni. (And when the fat guy rates something in the range of ice cream you know it’s a good tool.

Here is what he says about it…

Latest News

The final release of v2 is now available.
I’ve added a “repair” function which is designed to undo an expand operation on a base VHD when differencing VHDs are present. This is useful in cases where an admin accidentally expands a base VHD when Hyper-V snapshots are present.
To ensure data integrity in the case of an error, please make a backup copy of your VHDs before altering them with this tool.

Introduction
VHD tool is an unmanaged code command-line tool which provides useful VHD manipulation functions including instant creation of large fixed-size VHDs. The source code is included.

Requirements
A computer running one of the following Windows operating systems:
Server: Windows Server 2003 or above
Client: Windows XP or above
NTFS file system

Usage
VhdTool.exe /create <FileName> <Size> [/quiet]
VhdTool.exe /convert <FileName> [/quiet]
VhdTool.exe /extend <FileName> <NewSize> [/quiet]
VhdTool.exe /repair <BaseVhdFileName> <FirstSnapshotAVhdFileName> [/quiet]

Create: Creates a new fixed format VHD of size <Size>.
WARNING – this function is admin only and bypasses
file system security. The resulting VHD file will
contain data which currently exists on the physical disk.

Convert: Converts an existing RAW disk image file to a fixed-format VHD.
The existing file length, rounded up, will contain block data
A VHD footer is appended to the current end of file.

Extend: Extends an existing fixed format VHD to a larger size <Size>.
WARNING – this function is admin only and bypasses
file system security. The resulting VHD file will
contain data which currently exists on the physical disk.

Repair: Repairs a broken Hyper-V snapshot chain where an administrator
has expanded the size of the root VHD. The base VHD will be
returned to its original size. THIS MAY CAUSE DATA LOSS if the
contents of the base VHD were changed after expansion.

Known Issues
There are currently no known issues.

Frequently Asked Questions
How do I file a bug?
Click on the “Issue Tracker” tab and choose to “Create New Item”.

Examples
Create a new 10 GB fixed VHD in the current directory.
VhdTool.exe /create “c:\Program Files\MyApp\foo.vhd” 10737418240

Convert an existing flat image file into a VHD & do not output status to the command line.
VhdTool.exe /convert bar.img /quiet

Extend an existing fixed format VHD to a larger size.
VhdTool.exe /extend foo.vhd 21474836480

Repair a Hyper-V snapshot chain broken by expanding the base VHD.
VhdTool.exe /repair base.vhd base_EF2F9402-E85B-402F-A979-631CB287C2C4.avhd

http://www.tokeshi.com/node/5146