To install a new copy of Windows 7 Home Premium, click the Back button in the upper left-hand corner, and select “Custom (advanced)”. To save your files before installing Windows, back them up to an external location such as a CD, DVD, or external hard drive.
You’ll need to reinstall any programs using the original installation discs or files. You can choose to install a new copy of Windows 7 Home Premium instead, but this is different from an upgrade, and does not keep your files, settings and programs. Windows 7 Ultimate cannot be upgraded to Windows 7 Home Premium. If user attempts to perform an in-place upgrade to downgrade to lesser edition of Windows 7, an error similar to below will be displayed at compatibility report:
Upgrade is only possible one-way from the lower edition to higher edition of Windows 7, and not the other way round. Starter -> Home Basic -> Home Premium -> Professional -> Ultimate Windows 7 SKUs or editions have a hierarchy as below: For example, it’s impossible to downgrade from Windows 7 Ultimate to Windows 7 Professional or Enterprise, or from Windows 7 Professional to Windows 7 Home Premium or Home Basic. Windows 7 does not allow users to “downgrade” or convert from a more premium and more expensive edition to down-level, more basic and less expensive edition.
