What is Windows XP Activation

Most people are puzzled by the details of Windows Activation, and it is something that could affect them, for example, if they get a failed activation prompt.
So, here is article (link) that explains the details of Windows Activation. As a sample:

What is Microsoft Product Activation?
WPA is the licence that Microsoft uses that limits an install of a Microsoft product such as Windows XP. This would stop you from using your copy of Windows XP you used on your desktop to also work on your laptop.

Windows XP will generally remind you to activate your copy of windows about 30 days after installation (most common with Windows XP Home). This involves your computer contacting Microsoft and giving them some information about the current hardware you have installed. This returns a release code which will be recorded on your system.

What hardware does Windows check?
The system checks these ten categories of hardware:

* 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)
* CD-ROM / CD-RW / DVD-ROM