Microsoft has since clarified that testing Windows 10 will not automatically make you eligible for a free upgrade to the OS - see the latest story here.
So just who is eligible for a free copy of Windows 10? Even Microsoft appeared unsure over the past few days.
Now the dust has settled over ambiguous wording in an official Microsoft blog post, the general consensus is that you won't need a copy of Windows 7 or 8 to get a free upgrade to Windows 10.
Microsoft appears to have said - effectively - that anyone who is testing pre-release builds of Windows 10 will be able to get the release version for free.
Despite Microsoft tweaking the wording of the original post announcing the upgrade, to remove references to this final release version being activated, most people have settled on the idea that you will be able to get a free copy of Windows 10 if you are a part of the Windows Insider program.
Specifically Windows Insiders running the Windows 10 Insider Preview (Home and Pro editions), and with a registered Microsoft Account connected to their PC, will be able to upgrade to a final release build of Windows 10 from July 29th.
A later tweet by Gabe Aul, Microsoft's general manager of the operating systems data and fundamentals team, confirmed that registered members of the Windows Insider program who upgrade from a clean install of the preview edition will end up with a fully activated RTM copy of Windows 10.
Steve Kleyhans, vice-president of the Mobile and Client Computing Group at analyst house Gartner, believes those in the insider program will get a free upgrade.
"I think their intent was clear. They're trying to ensure that everybody on the tech preview program gets to keep going. They wanted to encourage them and say 'Yeah, you're going to get it'."
He believes the changes in the wording to the original blog post was simply Microsoft's attempt to give itself scope to protect itself against people exploiting the upgrade for piracy.
"I don't think anybody's trying to pull the wool over anybody's eyes here. When you start thinking about the implications of this broad statement you have think about how that could be misused in the market and I think that's why you saw some fumbling around in the blogs over the weekend."
He doesn't see a downside for Microsoft in allowing members of the Windows Insider program to upgrade to the release version.
"Why wouldn't they [provide this free upgrade] because most of them will be people who were predisposed towards Microsoft anyway, so they would be some of Microsoft's best customers. If they weren't helping to test it out they would be running Windows 7 or 8.1 anyway, so they would have qualified for the free upgrade."
While Kleyhans sees no difference between the version of Windows 10 that members of the technical preview will receive and that which will be available to users of Windows 7 and 8, what does differ is the timespan for the upgrade. While Windows 7 and 8 users have until July next year to upgrade Microsoft has said that pre-release Windows Insider versions of Windows 10 will stop working on October 15th.
Owners of Windows 7, 8 and 8.1 operating systems will see a Windows icon in their taskbar that will allow them to "reserve" their upgrade. The 3GB file can be downloaded from 29th July. The free upgrade will be available until July next year and those choosing to switch to Windows 10 can cancel their reservations at "at any time", according to Microsoft.
To upgrade using Windows Update users must be running Windows 7 (Service Pack 1) or Windows 8 (Windows 8.1 Update). Other Windows 7 and Windows 8 users will still be able to upgrade to Windows 10 by downloading the ISO image from Microsoft.
While Windows 7 Enterprise, Windows 8/8.1 Enterprise and Windows RT/RT 8.1 releases can't be upgraded in this way, Microsoft has said that "Active Software Assurance customers in volume licensing" will be able to "upgrade to Windows 10 enterprise offerings outside of this offer". Microsoft are yet to clarify when users of Enterprise versions of Windows will be able to move to Windows 10 Enterprise.
Kleyhans doesn't believe that many businesses, except very small outfits, would choose the free upgrade to Home or Pro editions of Windows 10 over paying for the enterprise version - due the enterprise offering letting businesses defer Windows 10's regular updates.
Nick Heath is chief reporter for TechRepublic. He writes about the technology that IT decision makers need to know about, and the latest happenings in the European tech scene.