How Windows Product Activation Works

Windows Product Activation or WPA is a license validation procedure introduced by Microsoft Corporation in all versions of it’s Windows operating system. WPA was first introduced in Windows XP and continues to exist in Windows Server 2003, Windows Vista, Windows Server 2008 and Windows 7 as well. WPA enforces each end user to activate their copy of Windows so as to prevent unauthorized usage beyond the specific period of time until it is verified as genuine by Microsoft. How WPA really works was a closely guarded secret until GmbH analyzed WPA using a copy of Windows XP RC1 and published a paper on their findings.

In this post you will find answers to some of the most frequently asked questions about Windows Product Activation.

Why activation?

Microsoft’s intention behind the activation is to limit the usage of it’s Windows operating system to only one machine for which the retail license is issued. Any other computer which runs on the same license must be disallowed from using the software. Thus WPA demands for activation of the product within 30 days of it’s installation so as to ensure that it is genuine.

What does “Genuine Windows” means?

The copy of Windows is said to be genuine only if the product key used during the installation is genuine. It means that a given product key (retail license) must be used to install Windows only on one computer for which the license was purchased. Thus if the same key is used for the installation on another computer, then it is said to be a pirated copy.

Exactly what information is transmitted during the activation?

When you activate your copy of Windows you are transmitting an Installation ID code to the Microsoft either by phone or Internet depending on the method you choose to activate. Based on this, the Microsoft’s licensing system can determine whether or not the installed OS is genuine. If it is said to be genuine, then the system will receive the Activation ID which completes the activation process. If the activation is done via telephone then the Activation ID needs to be entered manually to complete the activation process.

What information does the Installation ID contain?

This Installation ID is a 50-digit number which is derived from the following two data.

1. Product ID – It is actually derived from the 25-digit product key (the alphanumeric value that is printed on the sticker over the Windows CD/DVD case) that is entered during the installation of the operating system. The Product ID is used to uniquely identify your copy of Windows.

2. Hardware ID – This value is derived based on the hardware configuration of your computer.

The WPA system checks the following 10 categories of the computer hardware to derive the Hardware ID:

* Display Adapter
* SCSI Adapter
* IDE Adapter (effectively the motherboard)
* Network Adapter (NIC) and its MAC Address
* RAM Amount Range (i.e., 0-64mb, 64-128mb, etc.)
* Processor Type
* Processor Serial Number
* Hard Drive Device
* Hard Drive Volume Serial Number (VSN)

Thus the Installation ID which is a combination of Product ID and Hardware ID is finally derived and sent to Microsoft during the activation process.

How is the Installation ID validated?

The Installation ID needs to be validated to confirm the authenticity of the installed copy of Windows. So after the Installation ID is received by Microsoft, it is decoded back so as to obtain the actual product key and the hardware details of the computer involved in the activation process.

The Microsoft’s system will now look to see if this is the first time the product key is being used for the activation. This happens when the user is trying to activate his Windows for the first time after purchase. If this is the case then the Installation ID is validated and the corresponding Activation ID is issued which completes the activation process.

However Microsoft system will now associate this product key with the hardware ID of the computer and stores this information on their servers. In simple words, during the first use of the product key, it is paired together with the Hardware ID and this information is stored up on the Microsoft servers.

What if a computer running a pirated copy of Windows attempts to activate?

The activation fails whenever the copy of Windows installed is not said to be genuine. This usually happens when the product key used for the installation is said to have been used earlier on a different computer. This is determined during the activation process as follows:

During the validation of the Installation ID, the Microsoft’s system checks to see if the same product key was used in any of the previous activation processes. If yes then it looks to see the Hardware ID associated with it. The computer running a pirated copy of Windows will obviously have a different hardware configuration and hence the Hardware ID will mismatch. In this case the activation process will fail.

Thus for a successful activation, either of the following two cases must be satisfied:

1. The product key must have been used for the first time. ie: The product key should not have been used for earlier activations on any other computer.
2. If the product key is said to have been used earlier, then the Hardware ID should match. This happens only if the same computer for which the license was genuinely purchased is attempting for subsequent activation.

What about formatting the hard disk?

Each time the hard disk is reformatted and Windows is re-installed, it needs to be re-activated. However the activation process will be completed smoothly since the same computer is attempting for subsequent activation. In this case both the product key and the Hardware ID will match and hence the activation becomes successful.

What is I upgrade or make changes to my hardware?

In the above mentioned 10 categories of hardware, at least 7 should be the same. Thus you are allowed to make changes to not more than 3 categories of hardware. If you make too many changes then your activation will fail. In this case, it is necessary to contact the customer service representative via phone and explain about your problem. If he is convinced he may re-issue a new product key for your computer using which you can re-activate your Windows.

Some things WPA does not do

* WPA does not send any personal information at all about you to Microsoft. There is still an option to register the product with Microsoft, but that is separate and entirely voluntary.
* If you prefer to activate via phone, you are not required to give any personal information to Microsoft.
* WPA does not provide a means for Microsoft to turn off your machine or damage your data/hardware. (Nor do they even have access to your data). This is a common myth that many people have about Microsoft products.
* WPA is not a “lease” system requiring more payments after two years or any other period. You may use the product as licensed in perpetuity.

I have tried my best to uncover the secret behind the WPA. For further details and more technical information you can read the actual paper by Fully Licensed GmbH at
pa.txt. I hope you like this post. Pass your comments.

14 Responses to “How Windows Product Activation Works”

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    Dec 05. 2010

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  4. Noob

    Dec 19. 2010

    Hi man,

    this post is good.

    What are the security holes in the WPA process ?

    There are a lots of windows versions avaible on internet, are they safe ? What are the risks ?

    They are people who are selling “genious” key on Ebay, do you thing this is a safe wait to get cheap windows license ???

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    Dec 19. 2010

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