Upgrading to the free Windows 8.1 from Windows 8...

If you haven't done it yet, or it didn't go well for you, there's something about it that Microsoft hasn't explained very well. And that's about your Windows Key Codes - those five sets of five characters on the sticker on your box, or on the material with your disk, if that's how you got it.

When you've downloaded the ISO file for Windows 8.1 and used your favorite burning program, like ImgBurn, to burn that image file to a useable installation disk, and you've reset your BIOS to boot from disk instead of from its hard-drive, and you've put the install disk in your DVD drive, and the process has begun, one of the first things you will be asked for, after your choices of language and such are chosen will be your Windows Key Codes. 

Those will be the same ones you have already for your Windows 8, and here's an important note: these key codes are linked to your computer's Mac Address, and will only work for that specific computer. The Windows 8.1 itself on your disk can be used to install it on any computer, but that computer will need to have a legal version of Windows 8 on it, and you will need to use the Key Codes for that Windows 8 while installing your free upgrade to Windows 8.1. 

Also please note that if you are multi-booting, like I do, your free upgrade to Windows 8.1 doesn't have to overwrite your old Windows 8, if you have another partition on your hard-drive into which you'd like to put it. For example, on mine, I've replaced the system on another partition formerly holding PC-BSD, and this is quite acceptable because it is on the same computer with the same Mac Address (Physical Address) as the Windows 8 - and I didn't have to lose anything in my Windows 8 while doing it this way. Now, I can take my time and copy from Windows 8 into Windows 8.1 whatever I want to continue using.

"So what's this 'Mac Address' used for?" you ask. Here's a description I copied. A MAC (Media Access Control) address is a number that identifies the network adapter(s) installed on your computer. The address is composed of up to 6 pairs of characters, separated by colons. You may need to provide your MAC address to a router in order to successfully connect to a network.

In less technical terms, it is a little bit of code that is specific to your particular computer, and it identifies that computer to its connecting network, and no other computer should have your computer's exact set of characters, just as no other car should have your car's license number or V.I.N. - and it isn't transferable. If you get a new computer, it has a new Mac Address.