Avoid XP's Activation After a Reformat
From time to time, it's wise to reformat a machine if it starts acquiring too many quirky problems nobody seems to know how to fix, or if it's been so riddled by spyware, it would take days to clean, and even then, it would never work right again. So, to simply avoid the hassle of the activation process when you do format, follow these steps.
Before you reformat, go into the "C:\Windows\System32" folder, and copy the "wpa.bak" and "wpa.dbl" files to a safe place, such as a CD or Flash Drive.
After you finish reinstalling Windows, but before you reactivate, copy the two files you saved to the desktop. Next, boot up in safe mode by pressing F8 just before the Windows loading screen and selecting "safe mode".
Then go into the "C:\Windows\System32" directory and locate the two files there with the same name. If they exist, rename "wpa.dbl" to "wpa.nonactivated" and "wpa.bak" to wpabak.nonactivated
Now, put the "wpa.bak" and "wpa.dbl" you temporarily placed on desktop into the "C:\Windows\System32" folder. After a reboot, you should be all set to go..
Note that this will only work if you're running the same or very similar hardware as before.