Today I was tasked with upgrading some Windows 7 Home Premium PCs to Windows 7 Ultimate. For some reason the installer will not let you upgrade from Home premium to Ultimate and it tries to force you to do a clean install. I managed to find a way around this by editing some registry keys. Open Regedit and navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\WindowsNT\CurrentVersion And change: EditionID from HomePremium to Enterprise and ProductName from Windows 7 HomePremium to Enterprise Then re run your upgrade and everything should run as you expected! Original Blog Post