Kevin,
Wanted to get back to you about the google search topic I gave you..... the upgrade to W10Pro64 still works fine today if the current W7Pro64/W8Pro64 is activated and proper. There is still also another method if you use assistance as you'll see.
Why, you ask, can this still be?
I'm typing this from a HP workstation just upgraded today to W10Pro64 from an official install from my HP OEM COA W7Pro64SP1 installer DVD, and the install now has been upgraded without cost to W10Pro64 - without trickery or hassle. The answer is that it is a win-win-win for MS, HP and us.
MS wants as many of us on W10 as possible, HP wants that too and knows its base will upgrade later when ready to upgrade hardware, and we all want flexibility still on the issue of W7 vs W10 using our current hardware. There still is a MS income stream from upgrading by those who don't read up on the issue. Actually, if you do some reading you'll see that the upgrade fees are small potatoes to MS in the big picture.
My current new W10Pro64 install on this workstation is now activated with a digital license, which means later when I'm really ready to shift to W10Pro64 my workstation's UUID is forever registered centrally with MS as W10Pro64 activated, and I'll not need to enter any codes during a re-install of W10.
I'll add my usual sticker to the back of this workstation reminding me that it is W10Pro activated with MS centrally, and keep using my W7Pro64 build for now (recloned back on as of today). I have an Acronis clone of my optimized W7Pro64 build that I use...... but I am liking W10Pro64 more and more.