Microsoft has released a document which outlines supported and unsupported upgrade paths for Windows 7 SKUs. This table outlines the paths in the form of a matrix.
Windows 7 Upgrade Path
• Upgrades to Windows 7 from the following operating systems are not supported:
– Windows 95, Windows 98, Windows Millennium Edition, Windows XP, Windows Vista RTM, Windows Vista Starter, Windows 7 M3, Windows 7 Beta, Windows 7 RC, or Windows 7 IDS
– Windows NT Server 4.0, Windows 2000 Server, Windows Server 2003, Windows Server 2008, or Windows Server 2008 R2
• Cross-architecture in-place upgrades (for example, x86 to x64) are not supported.
• Cross-language in-place upgrades (for example, en-us to de-de) are not supported.
• Cross-build type in-place upgrades (for example, fre to chk) are not supported.
• Cross-media type in-place upgrades (for example, Staged to Unstaged or Unstaged to Staged) are not supported
Download : Microsoft.
Read: Windows 10 Upgrade Path and Process.