The issues below are more likely to affect retail bought and volume license clients.
If you are unable to enter the product key:
Press Windows key + X
Click Command Prompt (Admin)
At the command prompt, type the following commands:
slmgr.vbs -ipk xxxx-xxxx-xxxx-xxxx (allows you to replace the current product key with the specified)
xxxx-xxxx-xxxx-xxxx – represents your product key
Hit Enter on your keyboard
Exit the command prompt
Restart your computer
Try Activating again.
You were never running a genuine Windows 7 or Windows 8 license.
This issue particularly affects Windows 7 licenses. If you purchased your Windows 7 license from an auction website such as eBay or the Amazon, you might have mistakenly purchased a counterfeit copy. You can determine this by the product ID which determines your level support.
065, 066, 067, 068, 069 for Windows 7 Ultimate
220, 221, 222 for Windows 7 Professional
230, 231, 221, 232 for Windows 7 Home Premium
Click Start, right click Computer
Scroll down to Windows Activation and look at the PID It will look something like the following 12345-067-1234567-54321, the portion you are interested in is the three digit section, if it matches or is within one or two digits of the examples above you probably have an MSDN or TechNet key.
About MSDN or TechNet Product Keys
They are genuine Microsoft product keys, they are actually retail licenses, but it is intended for a particular product channel either the Microsoft Software Developer Network (MSDN) or TechNet for IT Professionals who pay a subscription fee. Although these licenses are intended for evaluation purposes, the great thing about them, unlike trial Microsoft software they do not expire. Because the agreement under which the subscription is provided is a single license, none of the software should be distributed outside of it. Even though it is $50,000 worth of licenses, it is for one person only to use and no one else. Unfortunately, regardless of the licensing terms, persons still abuse the program, either giveaway product keys or resell them on auction sites. Microsoft licenses it in good faith that customers won’t do so.
If you discover that your license is from MSDN or TechNet, what probably happened is, you bought an MSDN licensed key, which carries up to 10 activations unlike full packaged retail licenses which only carry 1 activation. The person who sold it to you probably sold it to 10 other persons. Somewhere along the way, one of those persons might have installed it on a second system, activated it, because it went past 10 activation threshold, Microsoft detected it that it was being abused and blocked the key from further use.
You can confirm that your software is genuine now. It’s quick and easy.