Volume licensing customers with a license for Windows XP Professional or Vista Business are eligible to use a prior version in place of the version they have licensed. Eligible Prior versions of Windows XP Professional include Windows 2000 Professional, Windows NT Workstation 4.0 or 3.51. Eligible prior versions of Windows Vista Business include Windows XP Professional and Windows 2000 Professional, Windows NT Workstation 4.0 or 3.51.
Microsoft has extended the above downgrade rights under Windows Vista Business Upgrade to allow you to downgrade to Windows 98 or Windows 95. If the customer exercises this right to use a prior qualifying Windows operating system for which there is Microsoft Plus! Software available, the customer may also use the appropriate Microsoft Plus! Software. For example, a customer who enrolls Windows Vista Business under Software Assurance may choose to use Windows 98 and Microsoft Plus! For Windows 98 instead of Windows Vista Business. Windows Millennium and Windows XP Home Edition are not prior versions of Windows Vista Business.
Wondering where you can find this information? It is located on Page 71 of the Microsoft Product List which you can download on the Microsoft Licensing website.
Thank you and have a wonderful day,
Microsoft US Senior Manager
Small Business Community Engagement
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