Hi Bob,
Sorry to hear your sad story of W10 upgrade installation problem. It would be helpful to have your machine specs so that we can customize a solution for your specific hardware. Make/Model of computer. Is it a Desktop PC or laptop? If Desktop PC is it an OEM PC (DELL, HP, ACER, ASUS, ETC.) or a self-built PC? Make/Model of your new hard drive?
Is the new drive a mechanical or SSD (solid-state)? This would be a good starting point. I've done a number of W10 installs and upgrades in my little computer repair biz and would be happy to step in. Kemical makes a good point. If you can get Win7 back onto your computer, and Win7 came originally pre-loaded from the factory, you mention that you have an upgrade disc, so that tells me that reading between the lines you don't have the original factory Recovery discs (DELL, HP, ACER, ASUS, etc.). Does that mean that your computer came with an earlier version of Windows such as Vista/XP/2000?? And that you upgraded to Win7 at some point or attempted to? Are you the original Owner of this computer, or did you buy second-hand or get it as a gift, handmedown, or other method. You can see that we don't really have a clear picture of the history of your hardware.
The main thing is that if you have a PC or laptop that was manufactured prior to 2006, it's unlikely to run with W10. A computer that old would have with XP from the factory; and those computers cannot be upgraded to W10 from W7/8/8.1/8.1.1; only a Clean Install. Additionally, you said you ran the 8.1 Pro preview. 8.1 and 8 both do some funny things with the disk drive, so one of the things that has to be done with a Win7 or Win8/8.1 install is to format the new disk drive to remove that special 8/8.1 "stuff" if you will from the drive in order to perform either a Win7 clean install or a W10 clean install. Most folks not in the computer biz who are home users are not aware of this.
While you are gathering your information to post back for us, I'll give you another tip to try and get you going. That is, when performing a W10 upgrade, if the upgrade fails, your license key, or right to convert your Windows license to a newer version never gets to the Microsoft Activation servers, and since you have a
PREVIEW version of 8.1 Pro and not an actual licensed version, the Activation servers never believed you bought an actual license. If you go into System Information and look, you'll see that your 8.1 Pro is not Activated, under the Activation section since it was a
PREVIEW license and not a live purchased license. This is tricky to fix, as I said, but you are missing 2 things; the first sounds like you didn't format the new drive to fully remove the 8.1 Pro from the drive prior to the W10 install. The second sounds like you are trying to upgrade from a
PREVIEW version of 8.1; that won't work either. As Kemical alluded to, you need to get a valid purchased Windows license onto that computer in order to get and run the W10 upgrade; once you do that, you'll get that machine's hardware with a legit key and your name registered on the Microsoft Activation servers. Confusing, huh?
That was another explanation, sorry,
the tip is that you need to get legit Win7/8/8.1/8.1.1 clean install media onto that computer! There are 2 ways to do this. The first way is to get a hold of the factory Recovery Discs from the manufacturer of your PC (this step won't work if you built your own custom PC, as only OEM computers have these available). Most modern computers, Vista and later (2007+) have either the set of discs needed to reset the computer to what we call "out-of-box" condition; in other words it will put back the version of Windows the factory originally loaded onto the original hard drive that came with your computer; along with all programs (bloatware) that the factory also loaded such as utilities, trial software like Office, etc. But, of course, not your data. That's your responsibility and hopefully you have that backed up to another computer in your home or external media. Modern computers also come with a built-in factory utility that lets you make your own set of bootable Recovery disks or USB media. A good example is the
DELL MEDIA CREATION TOOL, or the ASUS RECOVERY MEDIA ASSISTANT. Since you upgraded to the 8.1 Pro preview onto a new hard drive, those tools aren't there anymore for obvious reasons. The second way, is to contact the PC maker, best way is by phone, and call and order a set of
RECOVERY DISCS, if they are available for that model (this is another reason why we need your Make/Model information to help you with that task). Those Recovery Discs or Recovery USB drive run between
$29-$99 from the PC manufacturer, and all modern computer makers have these. They will ship to you in
2-3 weeks if your order to ship to a domestic, inside USA address, longer outside of US. You don't have to be a computer shop or business to order, this service is available to home users as well as businesses.
Another chink in the W10 installation is that Microsoft does not allow for upgrades from earlier versions of Windows than Win7; that's like
Win95/98/2000/XP/VISTA.
COMPUTERS IN THAT STATE CAN ONLY BE CLEAN INSTALLED WITH W10 MEDIA! This means that if you don't have a legit license--such as your 8.1 Pro preview; you can't get to there from here where you are. You already know this from your conversations with Microsoft support. Therefore, if you didn't get or create those factory
RECOVERY discs, you'll be stuck spending money to get them in order to get to W10.
Now, if you have a self-built PC, you can't buy
RECOVERY discs as clearly they are not available; you'll have to purchase legit W10 media ($199 like you said) from online retailers or from a computer store or repair shop. However, if you can get back to the version of Windows you originally installed on that original hard drive, and you have a license key for it in the Microsoft retail box packaging, you have a shot. If for instance the PC you have you bought a retail Microsoft Win2000 license and installed it and upgraded it multiple times; it may not work. Nor will W95 or W98. I believe you have to have had at least a WinXP license or newer. That allows for machines that are 14 years old. If yours is 9 years old or older (again made before 2006), the hardware will keep it from working anyway, so Microsoft will force you to buy newer hardware. This has been quite frustrating for customers where I live, in a rural area, who have many older machines, they have no upgrade path. Microsoft has never stated that Windows licenses are upgradeable forever, which you seem to think they are or should be. In the custom built scenario you could buy a copy of Win7 or Win7 Pro for $80-$140 or so on ebay or Amazon (make sure they are full licenses, and not upgrades as the one you have now is), install either one of those onto your PC's new hard drive, run the W10 upgrade, get registered with the MS Activation servers, and you're good to go!
However, this is almost as costly as buying a new W10 license as you observed. If you can live with W10 Home instead of W10 Pro; you can get them for around $100 online. So, it's 6 of one, half dozen of another at that point. If you built your PC, you'll have to put out some cash to get to W10, assuming your hardware isn't outdated as I explained in detail; but what other choices do you have?? Today's PCs only have a designed lifespan of about 5 years at the hardware level, and about 9 years at the software level.
Get back to us with your PC specs, and we can further advise you. If you have more questions, don't hesitate to ask.
Best,
<<<BIGBEARJEDI>>> 
