It seems that the Microsoft TechNet Windows 7 site does not show the download for the XP Pro Mode VHD.
The Connect site does have the download though:
With that in mind, those that are a part of the Windows 7 Beta program with access to the Connect Web site will be able to get that portion of the new operating system.
Note that the above download is shown for the x64 (64bit) version of the download. There is also a version for running on top of the x86 (32bit) version of Windows 7.
For now, we will be downloading only the x64 versions of Windows 7 and the Virtual PC Beta as it seems that the whole world is downloading right now!
Talk about a sssllloooowwww Internet connection and download speeds!
Microsoft Small Business Specialists
Co-Author: SBS 2008 Blueprint Book