Back up your XP Product Activation Files

After reinstalling XP, you have to go through the whole product activation again. Actually, there's a way around it. Before you wipe out the current installation, backup your product activation files and then you can restore them to the new installation.
Here's how:
Right click Start and click Explore.
In Windows Explorer, navigate to \WINDOWS\System32\ (usually on the c: drive but may be on a different drive depending on where you installed XP).
Copy the following files to a floppy, CD or second hard disk: wpa.dbl, wpa.bak.
To restore the files, start the computer in Safe Mode and copy them to the same directory (\WINDOWS\System32).