The free Windows 10 update

[Grayzzur]

ME doesn't count. That was just 98 SE with some updates built-in.  8)

[Karsten75]

There is a Microsoft blog post, updated at least 2 times, that clarifies the position eligible free upgrades for those running WIndows 10 previews - the Windows 10 insiders, so to speak. .

To use Anandtech's summary:

...  all Windows 7 and 8.1 customers are eligible for a free upgrade to Windows 10. This free offer extends for one year from the launch of Windows 10 which will be July 29th. If you are running Windows 7 or 8.1, you are eligible.

For those running a Windows 10 Preview:

• ...  you are a Windows Insider, and you want to stay in the program. After Windows 10 launches, the Insider program will continue, and there will be fast or slow rings for testers. The Insider builds are pre-release software and are activated with a pre-release software key. Eventually these builds will expire, however there will always be a new build with a new key before that happens. If you want to stay an insider after the launch, there is nothing to be done and you will continue to have an activated copy of Windows. However, from the post, there is one more point to add: "the Windows Insider Program is intended to be installed on Genuine Windows devices" so even though they are not checking, to be in full compliance, the device running the Insider preview of Windows 10 should be a licensed computer.
• ...  you have upgraded your Windows 7 or 8.1 computer to the pre-release Windows 10 build, but when the final build comes around you want to exit the program. As long as you started with a licensed Windows 7 or 8.1 PC, your PC will remain activated.
  
• ... if you want to exit the Insider program, but you are running Windows 10 from a clean install. In this scenario, you will be required to roll back to the original operating system, and then do the Windows 10 upgrade in order to get activated. Once activated, you can do another clean install if necessary.

[knucracker]

That last scenario is me (on the system I've used for testing).  There was no way I was going to "upgrade" a 5 year old installation of windows 7.  So I downloaded an iso of the pre-release and installed windows 10 clean.  Now sitting right on the desk next to the keyboard is the windows 7 installation DVD and the activation key for it. 

So rather than just letting me enter that windows 7 activation key after installing the release of windows 10, I have to install windows 7, no doubt download a couple gigs of updates and service packs, then "upgrade" to windows 10.  Then blow it all away and install windows 10 from scratch.  I'm sure I could just upgrade from the clean install of windows 7, but I also have no doubt that will end up with perpetual wasted disk space and some lingering issue that will plague me for the rest of that machine's lifetime.

On the matter of staying in the insider program... I'm sure a lot of people will continue to do that.  It is a way to get "free" windows for the foreseeable future. I also dread this from a support perspective.  Various windows and patch levels are already bad, now there will be large numbers of beta testers running some half broken build of windows... and I'll get support email saying "Creeper World 3 crashes.... etc, etc.  And oh, I'm on the latest fast ring release of windows 10 released 2 hours ago".

I already get this... about build 10130 of the windows 10 beta. 

[Asbestos]

When installing Windows 10, does it delete all of the files and such you have on the old system?

[thejoe66]

I wish I had a genuine copy of windows so i could upgrade,