Microsoft is enabling Windows users who buy Windows subscription plans like Windows 10 Enterprise E3 and E5 through the Cloud Solution Provider (CSP) program to upgrade from Windows 7 and 8.1 for free.

Credit: Microsoft

"Customers subscribed to Windows 10 Enterprise E3 and E5 as well as Secure Productive Enterprise E3 and E5, can now upgrade their Windows 7 and Windows 8.1 PCs and devices to Windows 10 without the need to purchase separate upgrade licenses," said Microsoft officials in a January 19 blog post detailing the new option.

Here's a quick refresher on some of the terms above.

Windows 10 Enterprise E3 and E5 are two new subscription plans for Windows Enterprise that Microsoft introduced last summer. They are largely aimed at small/mid-size business users. Windows 10 Enterprise E3 costs $84 per user per year, or $7 per user per month; E5 costs $168, or $14 per user per month. Both plans are available directly from Microsoft through its volume licensing program and through its CSP partners.

Secure Productive Enterprise E3 and E5 are additional subscription plans that include Windows 10 Enterprise, Office 365, and the Enterprise Mobility + Security suite.

Microsoft is hawking the new ability to get a free upgrade from Windows 7 and 8.1 to Windows 10 through these programs as targeted at customers who have yet to purchase a new Windows 10 device or "who missed out on the free upgrade to Windows 10 campaign."

(Don't forget: Microsoft still does quietly offer the option to get Windows 10 for free using Windows 7 and 8 product keys, even though the free upgrade offer officially ended on July 29, 2016.)

The Windows 10 upgrade licenses issued via this new offer are perpetual and associated with specific devices. "This means the license will not expire or be revoked if the customer chooses to end their Windows cloud subscription in the CSP program," Microsoft blog post says.

The perpetual licenses are for the Pro versions of Win 7/8.1 to Windows 10 Pro, with a simplified step-up capability to go from there to Enterprise.

The new upgrade option is rolling out now and tenant admins with Windows subscriptions in CSP should see these new options in the Office 365 Admin centers over the next 48 hours, according to Microsoft.

Microsoft seems to be trying to drive more business to its CSP partners as of late. Recently the company announced that Azure and Azure Pay-as-You-Go will be available to new customers through CSPs and not directly from Microsoft via the Microsoft Products and Services Agreement (MSPA).

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