New
#11
Thanks this route worked for the download portion of the upgrade.The ISO is free, and available for download.
Windows 10
You won't need a product key if you install it as an upgrade over an activated Win 7 or 8. You shouldn't be asked for one, and it will be activated.
I don't know what your problem might be. The E6600 supports the NX (no execute) bit, and I believe that it has the rest of the required properties. (As others have written, if it runs Windows 8, it meets the requirements for 10, by definition.)