win10

On a totally new build--everything new--can I use the product code I now have (free win 10) or do I have to buy the win 10 disk to get the product code?

It's my understanding the product code from the old machine is digitally registered/activated with Microsoft but the new computer won't be recognized in their database and won't activate so purchase of the product to use on the new machine will be necessary. At least that's what I'm seeing in planning for my next Custom build.

robert said:

On a totally new build--everything new--can I use the product code I now have (free win 10) or do I have to buy the win 10 disk to get the product code?

If you had a full retail version of Windows on the old computer (either full retail Windows 7, 8 or 8.1 upgraded to Windows 10 or full retail Windows 10) then you can MOVE the Windows 10 from the old computer to the new computer. You will have to uninstall (remove) all Windows from the old computer (just format the HDD/SSD or move the HDD/SSD from the old computer to the new computer) and then you can install Windows 10 on the new computer. To activate it:

Microsoft Account - Link to Digital License on Windows 10 PC - Windows 10 Forums
Activation Troubleshooter - Use in Windows 10 - Windows 10 Forums

If that doesn't work, then you will have to call Microsoft and tell them you moved a full retail Windows from an old computer to a new computer.

If the Windows on the old computer was OEM - or if you want Windows on both the old and new computers, then you have to purchase Windows for the new computer.