That means Windows 8 Pro licenses supplied by OEMs include the right to downgrade to Windows 7 Professional and Windows Vista Business, but not Windows XP Professional, Horowitz says. (If you want to downgrade to Windows XP then you would have to add Software Assurance to the new Windows 8 Pro machines within 90 days to gain the volume licensing's unlimited downgrade rights, he says.)
To make things more confusing, there's also the issue of edition downgrade rights. Edition downgrade rights are provided for only a few Microsoft products such as Windows Server and SQL Server. They are commonly used at the same time as version downgrade rights to allow you to deploy an earlier version of a different edition of the product--for instance downgrading to SQL Server 2008 R2 Standard Edition on a computer that is assigned a SQL Server 2012 Enterprise Edition license, says Horowitz.
It's not immediately obvious why you would want to exercise edition downgrade rights, but one common reason is when a particular edition is no longer offered. For example, there is no Enterprise Edition of Windows Server 2012, so to downgrade to Server 2008 R2 Enterprise Edition you would have to acquire Windows Server 2012 Standard or Datacenter Edition and exercise your edition downgrade rights.
The other reason is to simplify virtualization. Higher-edition Windows Server and SQL Server product licenses combine the right to run multiple instances of the software within virtual machines on the licensed hardware with edition downgrade rights. That means you don't need to worry about which particular edition you are running on each individual virtual machine, Horowitz explains.
Beware Possible Compliance Pitfalls with Windows Downgrades
There's a couple of common downgrade scenarios that are worth being aware of that could cause you to fall into noncompliance unwittingly. One of these revolves around lack of edition downgrade rights: If you buy Office Professional Plus, for example, but choose to deploy Office Standard, you could be in trouble.
That's because, surprisingly, Office Professional Plus does not include edition downgrade rights to the lower edition. If your company were to be audited in this scenario, you would have to buy Office Standard licenses to match your deployment.
Another common and potentially expensive mistake concerns a version mismatch with CALs. Here's the problem: all your CALs must be the same or a higher version than the servers that your clients access--Windows Server 2008 CALs allow access to Windows Server 2008 and Windows Server 2003 R2, for example.
If you buy a copy of Windows Server 2012 and downgrade it to Windows Server 2008, and you have Windows 2008 CALs, then your company is in compliance. But all it takes is someone in the IT department upgrading a Windows Server 2008 installation back to Windows Server 2012 (which you have a license to do) and suddenly all your clients that can access that server are now out of compliance.
Sign up for CIO Asia eNewsletters.