There is a supported in-place upgrade path from Windows Server 2003 x64 to Windows Server 2008 x64 or even Windows Server 2008 R2 x64 Why it could not be also the case for an in-place upgrade from Windows XP x64 to Windows Vista x64 ? Could an ephemeral path transiting via the use of NTswitch/TwearkNT to change the personality be considered or others tricks ? What are the current knowledge on this topic ?