If you haven’t backed up your Windows XP system, or haven’t created a master image that you can restore in the event of an irrecoverable system failure, and you haven’t made any changes to the hardware that would invalidate the old activation code and make it necessary to reactivate Windows XP, you can store the two files that contain the Windows Product Activation (WPA) data on a floppy disk, and copy them to the system after reinstalling Windows so that no activation is required from Microsoft’s site or by telephone.
The two files are called Wpa.dbl and Wpa.bak. And they’re located in the C:\Windows\system32 folder (if Windows is installed to its default Windows folder and not to a folder with a different name of the user’s choosing).
You should reinstall Windows XP. During the process, you should refuse the option to “Activate now”. You should then restart the computer and press the F8 key to bring up the Advanced Boot Options menu, and then choose to boot into Minimal Safe Mode. You can then open My Computer, click on the A: drive and copy the two files on the floppy disk to the C:\Windows\system32 folder.
Note well that you should not do this if you have made changes to the system’s hardware that would require Windows XP to be reactivated on the web or by obtaining the new code from Microsoft over the telephone.
The two files contain a description of the system’s hardware and the activation code that Microsoft generated from its site or provided by telephone, both of which are encrypted. At each system start-up, Windows XP decrypts (unencrypts) the description and checks to make sure that the hardware matches the recorded description. The details that are recorded include the serial numbers of the hard disk drive(s), and the MAC address that every Ethernet network card has. A user therefore cannot copy the two activation files from a system that has the same hardware, because although the make and models of the hardware are the same, the identification numbers are different.
A newly installed copy of Windows XP allows its user to activate it automatically from Microsoft’s site without having to obtain the activation code from Microsoft over the telephone. But if you attempt to reactivate the same copy of Windows XP within 120 days, you have to obtain the activation code over the telephone.
To do that you need to know what the Windows XP product key (also known as the CD key) is. It should be recorded on the licence sticker that is provided with with the Windows CD, which its user is supposed to stick on the computer’s case. If this has been lost then it’s not as easy as it was in Windows 95/98/Me to find out what the key is, because in Windows XP and Windows 2000 it is encrypted and not stored in plain text, as it is in the Windows 9.x versions. To find out what it is, you can use a utility specially designed to do so, such as Magical Jelly Bean’s Keyfinder from http://www.magicaljellybean.com/.