While Windows 7 will usually be automatically activated when you install it, sometimes you will have to enable it manually. Enabling Windows 7 will certify that the copy of Windows is only used on your computer hardware, so this can help combat piracy. If you recently purchased a computer, or you cannot connect to the internet after installing Windows 7, you may have to manually activate a copy of Windows 7. That is why you will be given a valid serial number if you happen to need to activate the Windows 7 by yourself.
However, as you might already know that now you can install Windows 7 without having to buy it from an official dealer. You can simply download Windows 7 for free. However, unfortunately, most of the Windows 7 that you can download on the internet is also in the trial status that you still need to activate it to make it permanent. If that is the case, that you need to use a Windows activator to be able to install it completely free. For example, you can check out some of the Windows activators for Windows 7 on http://windows7activator.org.
So, usually, to activate windows 7, you have to enter a valid serial number and to get this serial number you have to buy with the price of hundreds of thousands of dollars. When you first install windows 7, you can ignore to enter the serial number and you will be given 30 days for the free version. As for the rest, you have to activate it with a valid serial number. So, it means that even though you have already gotten the Windows 7 for free on the internet, you actually still need to pay for the serial number. Then, it means you do not get the Windows operating system for free. However, it will be a different case if you also use a Windows activator. A Windows activator will be able to allow to activate the Windows without a serial number.