"So no downgrade rights to XP. Also note that the soon-to-come Office 2013 will not support XP. So we can see they are trying to strangle the life out of XP," said Kenny Chan, a technology specialist for CDW, in message earlier this month on a dedicated to Microsoft licensing professionals.

"What I don't know is how long Microsoft will keep XP available for download on VLSC for volume licensing customers after the debut of Windows 8," Chan added. VLSC (Volume License Service Center) is the online portal for companies that have signed volume licensing agreements with Microsoft.

Unlike consumers or small businesses, corporations armed with enterprise licensing agreements, including the annuity-like Software Assurance, are allowed to downgrade from any version of Windows to any previous edition.

Downgrade rights became noteworthy after Windows Vista's 2007 launch when many users, frustrated at that edition's problems, .

Traditionally, downgrade rights are available only from OEM copies of Windows, those that are pre-installed by computer manufacturers. It looks to be the same with Windows 8: The software license for the retail version of Windows 8 Pro omitted the section on downgrades.