windows 10 and clean install

[comda]

Alright. I do not understand how this works.
 I have a PC and a mac. Both are running windows 7. The macbook runs Home (dual boot with OSX) and the desktop Pro.

I downloaded the windows 10 media creation tool as i want to have the ISO so i can make a fresh install. But this page:
http://windows.microsoft.com/en-us/windows-10/media-creation-tool-install

states that and i quote
"If you upgraded to Windows 10 on this PC by taking advantage of the free upgrade offer and successfully activated Windows 10 on this PC in the past, you won't have a Windows 10 product key, and you can skip the product key page by selecting the Skip button. Your PC will activate online automatically so long as the same edition of Windows 10 was successfully activated on this PC by using the free Windows 10 upgrade offer. "

SO my question is, i have to first do an upgrade then if i want a clean install i format my PC and dont use a key code? how will MS know its the legit upgrade? and If after i do the windows 10 upgrade with my windows 7 key (im assuming thats how it works) and i dont like 10 can i still use that key for 7?

[Geek-9pm]

So many questions. Wait for the best answers.

Meanwhile, here is something g you can try.
Get another hard drive, even an older one.
Put windows 7 on it. Activate it. Install Windows 10.

If something goes wrong, you still have the drive with your stuff .

Please come back.

[Salmon Trout]

if i want a clean install i format my PC and dont use a key code? how will MS know its the legit upgrade?

The Microsoft activation server will recognize your machine because it has already stored your unique hardware ID.

and If after i do the windows 10 upgrade with my windows 7 key (im assuming thats how it works) and i dont like 10 can i still use that key for 7?

Your Windows 7 key will still work if you decide to reinstall.

[Sanddy1911]

Hey comda
Unfortunately firstly you have to update your pc so that your existing win 7/8 key will be converted to win 10 of the same version after that you can install fresh copy of Windows through various media. Hope this helps

[Fitster]

Hi, didnt know where to ask. So my problem is that i started to install win10 and dont know how but switched off my pc. Happened this:

Can anyone help me?

[Geek-9pm]

Do you have a backup?
Here is a link to the ISO for Windows 10.
https://www.microsoft.com/en-us/software-download/windows10ISO
Using your other computer, burn it to a DVD and try it. When it finds your bad install it will attempt a repair.
If your select "Custom  Install" you could o format the partition.

At stated above by Salmon Trout, the MS server will know who you are.

Here is a link that may answer some question you have.
http://www.howtogeek.com/224342/how-to-clean-install-windows-10/