If you are a genuine Windows XP user and reinstall windows after some minor hardware changes, XP will ask you re-activate your copy of windows. I feel this is a total waste of time of user and causes incontinence. To avoid this problem, you can do the following:

1. Go to folder C:\WINDOWS\system32 and look for a file named wpa.dbl
2. Copy this file to a floppy or CD
3. Now when you reinstall the OS, simple replace this wpa.dbl file from old installation to the new one.
4. Replacing may cause a problem and not get replaced by showing error of “file in use”, so what you do is start the computer in safe-mode (pressing F8 at startup) and then replace the file.
5. Done! You don’t need to activate now!
This trick doesn’t mean that you can install your copy of OS on as many computers as you want, it will only work for one from which the wpa.dbl file was taken.