It's just about time for Microsoft to launch its expected Windows 8 upgrade program.

For the past several years, in order to keep PC sales from falling off a cliff in the months shortly before Microsoft and partners are poised to roll out new models running a new version of Windows, Microsoft has offered an upgrade program. Via these programs, customers who buy PCs running the current version of Windows (in this case, Windows 7) get "coupons" allowing them to get a free version of the next OS release (Windows 8) once it is generally available.

Sources

Here are some of the particulars of the coming Windows 8 program, according to my contacts. (The upgrade offer image above is from materials Microsoft is said to be providing to some of its OEM and retail partners about the coming program, according to my sources.)

Microsoft will make the so-called "Windows 8 Offer" available to consumers buying a Windows 7 PC running Home Basic or higher, allowing them to obtain Windows 8 Pro once Windows 8 is available. The Windows 8 Pro SKU is for tech enthusiasts and business/technical professionals, and includes encryption, virtualization, PC management and domain connectivity, as well as support for a separately priced Media Pack for Windows Media Center.

Seemingly because the offer is for the more feature-rich Pro SKU, rather than the entry-level Windows 8 (consumer) one, the offer won't be "free." There will be some fee attached to the coupon, but there's no word on what that's going to be (so far). The upgrade offer will start on or around June 2, 2012 -- right around the time Microsoft delivers the Release Preview (Release Candidate) of Windows 8 -- and last through January, 2013. By kicking off the upgrade program in early summer, Microsoft is hoping to capitalize on the back-to-school market, even though Windows 8 may not actually be available (and isn't expected by most Microsoft watchers to be) by the time students start school.

I asked Microsoft about the pending Windows 8 Offer, and company representatives declined to comment.