Essentially, Yes, you can as long as your W8.1 was Activated before the Upgrade and it was done between July 29 2015 - July 29 2016
: the period of the free W10 upgrade 1 year trial period, and the W10 was also showing as Activated.
The exceptions are (1.)
If your W8.1 was NOT
Activated during the 1 year trial period when you performed the upgrade, and therefore your W10 was also NOT
Activated; and (2.)
If your W8.1 was Activated during the 1 year trial period when you performed the upgrade, but you never checked your W10 Activation status and the W10 was NOT
Activated, or it was NOT
Activated and you didn't know if it was or wasn't and therefore didn't install it correctly or Activate it correctly.
Either of the above exceptions might have resulted in the incorrect or non-registration of your computer with the Microsoft Activation Servers where W10 licenses are stored. Once you install the W10 onto your new hard drive, you can check to see if your W10 is properly activated by following these instructions here: How to make sure your free copy of Windows 10 is activated
If we assume for a minute that you did indeed do your 8.1->10 upgraded during the 1 year free trial period as above (which about 300 million other users did also), and your W10 was properly Activated, all you have to do is download the free MCT tool from Microsoft's website and burn the W10 installation media to DVD disc or USB drive and perform a Clean Install of W10 on the new drive. Instructions to get the tool and download the W10 ISO file are here: Windows 10
If your upgrade was then indeed done during the 1 year trial period, this tool will preclude your W8->W8.1->W10 upgrade process being repeated again. I have 8 machines running W10; and only 1 of them was a legit upgrade during the 1 year trial period; (my Windows7 Sony laptop). I never had to pay to Activate that computer.
I have 3 other W10 computers, I did have to pay for W10 licenses for since I didn't attempt to Activate them until after the 1 year trial period was over; after the July 29 2016 expiration date. I currently then have 4 computers of 8 running W10 Activated legit licenses. The rest are test machines.
This information is given so you can more fully understand the upgrade process. The important thing to realize is that if your W8/W8.1 was Activated prior to the upgrade, and especially if your computer came from the factory with a legit W8/W8.1 license and you upgraded to W10 during the W10 free 1 year trial period; your path to recreate a W10 Activated license on your new hard drive is quite simple. Download the MCT tool from Microsoft as in the above paragraph *wiping out your W8 you just put on there*, and the W10 install program will recognize your computer hardware and contact the Microsoft Activation Servers and properly reactivate your W10 license!
It's also important to run the free Microsoft W10 COMPATIBILITY TEST
that's included with the W10 MCT tool install program to check if your system has any outdated or incompatible hardware, programs, apps, or drivers that will cause the MCT tool install program fail to reinstall your W10 on the new drive.
Instructions on how to run this test are here: Get Windows 10 app - Check Compatibility Report for Windows 10 If you don't remember running this program when you upgraded your computer to W10 before, or you are unaware of the necessity to run it--please consider that it's very important for the success of the W10 install to complete.
If there are issues in the Test result report, you must take care of them. Be aware that there have been over 10 new sub-releases of W10 since your W10 upgrade if it was installed back in July 2015 or thereabouts, and even if your W10 upgraded fine back then, with the newer versions of W10 out now, that may not be the case with your W10 Clean Install to the latest version (v1607 b14393.447
This is a really good idea to run this program to reinstall your W10 on the new drive then! You can avoid the pitfalls that many folks have when tried to reinstall their W10 onto a replacement hard drive in this manner.
I've done several drive replacements on W10 computers such as yours that were running Activated versions of W10 and not Activated. In the case that your situation falls into 1 of the 2 exception cases I mention at the beginning of this Post, you will most likely need to purchase a legit W10 license key through a Microsoft retailer such as Best Buy or Staples, or an online retailer such as Amazon, newegg, or Redbox Software.
I did this for 2 of my non-Activated W10 machines as I mentioned and it worked just fine.
This is probably more information than you wanted; but we get this question frequently now, as people trying to install newer Microsoft software such as MS Office365, MS Office2016, or 3rd party software such as Adobe CS3 Elements, or Photoshop, or whatever can get errors when trying to install onto a non-Activated copy of W10. So folks who have been running the W10 free trial for a couple of months or up to 1-1/2 years for free [non-Activated] now find that they MUST
pay for a license for their W10 in order to run their new program on that computer. Of course, people will want to run their W10 forever for free and don't want to pay for a legit license for their OS. There are a lot of reasons why that is and I won't go into that here as most reasons are obvious.
Your situation is quite simple-if you know your W8.1 was Activated, and you DID
upgrade to W10 during the 1 year free-trial, you can get your W10 onto your new hard drive by W10 Clean Install using the MS MCT tool download as per my link above. And you're all set to go with your W10 again!
For the exclusions listed, in most cases you can reinstall, but you'll be required to purchase a legit W10 license at some point on that computer.
I hope that answers your question fully. If you have any questions, feel free to post back here to this thread. Many of us including myself are W10 Insiders; folks who volunteered to test out W10 for MS before it's release on July 29, 2015.
I've been running it for 2-1/2 years. We can all answer most question you might have.
Best of luck, <<<BIGBEARJEDI>>>