Intel® Compute Stick supports Windows® 10 32bits and 64bits; it is necessary to pay for this Operating System upgrade, and the only way to change it would be through Microsoft.
Many thanks for your update, I already have a Windows 10 - 64bit product licence code that I can use.
I am interested to know the steps required or details of the upgrade process ie. is it just "load and go" from a Windows 10 download or a more complicated process than that.
At the end of this site you will find Related Topics in regards How to Upgrade to Windows 10 and Upgrade to Windows 10 FQA.
I suggest you to create Windows Recovery Media: http://windows.microsoft.com/en-us/windows-8/create-usb-recovery-drive
Here you can see the steps to create USB bootable drive: https://www.microsoft.com/en-us/software-download/windows10
Please let me know if it helps you.