As far back as I can remember there have been virtual image formats for disks. In the days of floppy drive it was the .IMG files I used to backup my floppy’s to hard drive followed by .lSO files for CD ROM images and more recently the .VHD files for virtual hard drives as supported by Virtual PC, Virtual Server, the iSCSI provider, Hyper-V and most recently the introduction of boot from VHD with Windows 7 as described in detail in Aviraj Ajgekar’s recent post.
Since Microsoft made the VHD Image Format Specification available to third parties under the Microsoft Open Specification Promise and I would like to think that this has now become the de facto standard disk imaging format with the likes of Citrix XenServer and Sun’s VirtualBox supporting it. That's not to say its Microsoft's only bootable images format with the most notable alternative being the .WIM file introduced with and used as part of the deployment tools for Vista.
This brings me to the self describing utility WIM2VHD that was recently released by Mike Kolitz to convert .WIM files into .VHDs. Perhaps bringing closer the utopian idea of unified disk image formats. The software is available for download from the MSDN Code Gallery as WIM2VHD and includes some decent documentation. For more information check out Mike’s blog post.