For products with the Windows 7 Professional downgrade:
This system is preinstalled with Windows 7 Professional software and also comes with a license and media for Windows 8 Pro software. You may only use one version of the Windows software at a time. Switching between versions will require you to uninstall one version and install the other version. You must back up all data (files, photos, etc.) before uninstalling and installing operating systems to avoid loss of your data.

Windows 7 disclaimer:

Systems may require upgraded and/or separately purchased hardware to take full advantage of Windows 7 functionality. Not all features are available in all editions of Windows 7. See http://www.microsoft.com/windows/windows-7/ for details.

Windows 8 disclaimer:

Not all features are available in all editions of Windows 8. Systems may require upgraded and/or separately purchased hardware to take full advantage of Windows 8 functionality. See http://www.microsoft.com/windows/ for details.