Helping people with computers... one answer at a time.
Product keys are used to activate or enable a purchased application. You can often find product keys used on your machine with a special application.
It's important to save that box, sleeve, or whatever else your product key was originally distributed on.
Under certain circumstances, you can retrieve it from the system that it's installed on, but unfortunately, under other circumstances, you cannot.
I'll look at a couple of tools that you can use to see if it's available for you.
Keyfinder from Magical Jelly Bean is a free utility that will display your Windows product key.
Be sure to say "no" to the additional toolbar that the Keyfinder install offers you.
Once run, Keyfinder gives you the information for the current system:
I've obscured my information, but you can see where your CD key would be displayed.
Keyfinder is free and works primarily only with Windows keys. On the download page, they do offer another product which is not free, which claims to display product keys from a wide variety of products.
Belarc Advisor is a PC auditing/inventory tool that actually displays a lot of information about your computer.
Download, install, and run Belarc and it'll start by taking a few minutes to analyze your computer. When done, it displays its results in a local web page in your browser.
To the right is an example of the report generated for my machine. As you can see, it's quite lengthy and includes a lot of information about the machine, its hardware, and the software that's installed on it.
Included in the middle of all of that information are the product keys:
Once again, I've obfuscated my own keys, but you can see that Belarc displays keys for a wide variety of installed programs.
Write down all of your keys and keep them somewhere safe.
Now. Before you need them.
As an example, I have a spreadsheet that I keep of all of the products that I've purchased and their activation keys. Should I ever need to reinstall a program, I have that information readily available. (Naturally, I keep it secure and also back it up regularly.)
In many ways, product keys are the product. It's not uncommon for the software to be readily available, but without a product key, it either won't activate or will deactivate after a trial period.
Don't lose your keys.