I just got the idea as it is still working and downloads WDP. Here's the URL: Code: hxxp://win.esd.microsoft.com/pr/WCPDL/8A9D4FDFF736C5B1DBF956B89D6C8FDFD925DACD2/735224-wdp_amd64_prerelease.esd?t=96c791af-e27a-4e3d-84a4-f1a8a993997d
Actually, it's a modified version of the download/install tool from the Connect-hosted InstallFair (shortly after BUILD itself). The version used for the InstallFair (a mix of the WDP and never-leaked 8112) was designed to test upgrades from Windows 7. Other than MSE being borked, the process was flawless (which was, in and of itself, completely unexpected - would anyone expect an upgrade from a production OS to a mid-level alpha to actually work?). I wouldn't be surprised if a public version of this became available for *all* the various Previews, and even the RTM, as it's basically C2R (used by Office 2010 today) meets Windows (or even Microsoft's response to Wubi/UNetBootIn, which is used by many Linux distributions today, including Ubuntu).
Besides, even if it installed/downloaded *nothing*, it makes a great rough software-checker (to find out what should work, and what won't) with the WDP or later. Here's my report (given as an example): VirtualCloneDrive won't work (no surprise - superseded by Windows Image Mounter in WDP and later) - it is, in fact, the only failure. AMD's Catalyst will require an update to the WDP-or-later specific version (that is also unsurprising). Everything else will work (MSE requires uninstallation prior to upgrades - however, this is due to MSE/Windows Defender in the WDP and later having major code differences; Windows Defender and MSE use the same definition files, though).