How do I find the product key for Windows 8.1

A lot of these issues have become moot recently with the update to Windows 8.1 Update.

   The issues a lot of people were having were not being answered correctly because many thought that they were talking about systems that came with Windows preinstalled . Not all cases were. 

   You could have bought a computer with Windows 8 preinstalled on it. In which case you had a manufacturers volume license key, or you could have bought a copy of WIndows 8 , in which case you would have had a full version license key .

    In any case , when Microsoft updated Windows 8 to Windows 8.1 .... they forgot about those that had purchased an individual copy of Windows 8 . Those people wanted to make a backup of Windows immediately , or to make reinstall media on either DVD or USB drive . They couldn't make backups at all because the backup feature required a Windows 8.1 key ..... which we did not have. You could make the install DVD or USB ... but they were useless because upon trying to reinstall with them .... you needed a Windows 8.1 key ..... which we did not have.

    That upset a LOT of people. So in when they put out the update ( Windows 8.1 Update ) , they set it up so that your Windows 8 key would work to make DVD and USB restore media , and fresh install media .

    They seem to have learned from that lesson apparently . From what I have been told , when the free Upgrade to Windows 10 comes out soon , we will be able to make clean install media right off the bat.

   And apparently , as soon as we upgrade , we will be given a key FOR that upgrade , so if we do need to reinstall , there will not be this huge hassle again.

As I said the situation is slightly varied because if the problems you have highlighted. However the point is a new PC comes with Windows pre authenticated using a special key issued to each manufacturer. This bypasses a key function of the anti-piracy methods used by Microsoft so they blocked any attempt to use such a key with a DVD based install all of which required authentication after installation. With the key embedded in the BIOS presumably considered unhackable local authentication becomes viable.

You cannot blame Microsoft entirely. Leaving aside their actual wealth a vast sum was being lost by software pirating which they have every right to try and reduce. Where they have failed is the fact that these methods impinge on legitimate users as well. They seem to struggle at the moment with joining up their processes. Reset is great but it should not require ANY files from another source which you might not have.

Thanks, I understand all that. But...if you make a downloadable USB image from MS, they specifically state it cannot be used without the product key.

How can there be no value in the key? According to MS,  I cannot recover without it.

The key is embedded in the UEFI system BIOS. If you use the correct "Edition" of Windows 8.1 "Edition" with Update 1 installation media the key will be automatically input and you will be taken to the license agreement screen. If the wrong Edition is selected you will be asked for a product key. On the guide I linked to earlier I highlighted all the common difficulties and workarounds users are experiencing with this are due to the many sub editions Microsoft made and the lack of clear distinction between the labels.

Thanks, I understand all that. But...if you make a downloadable USB image from MS, they specifically state it cannot be used without the product key.

How can there be no value in the key? According to MS,  I cannot recover without it.

They don't give the key because there was no value in having it.

Things have changed slightly but essentially the key would only be valid for the image pre-installed by the manufacturer, it will not activate ANY disk based install.

Even with Windows 7 which had a readable COA label the key used by the manufacturer to build the system was not the same as appears on the label.