If you have access to your Windows XP system (or a backup) you need to grab a copy of the activation files before you reformat and install a fresh copy.

The information about the current activation is stored in an encrypted database file named Wpa.dbl, which you can back up and then restore once you've reinstalled XP. Remember that this technique only allows you to reinstall XP on the same computer--if you've installed new hardware (like a hard drive) this may or may not work. That's the catch 22, no hardware changes.

Here's how to back up the Wpa.dbl file:

1. Insert a blank, formatted disk into the floppy disk drive or insert a USB flash device.

2. Using Windows Explorer, navigate to the C:\Windows\System32 folder.

3. Right-click the Wpa.dbl file and select Send To the 1.44 Floppy or USB device.

You can then reformat the hard disk and reinstall XP. Once the installation procedure is complete, follow these steps to restore the Wpa.dbl file:

1. Restart the computer.

2. Press [F8] when you see the message Please Select The Operating System To Start.

3. From the Windows Advanced Options Menu, select Safe Mode.

4. Using Windows Explorer, navigate to the C:\Windows\System32 folder.

5. Rename the new Wpa.dbl to Wpa.new.

6. Insert the disk that contains the backup into the 1.44 disk drive or plug in your USB device.

7. Copy the Wpa.dbl file from the floppy disk to the C:\Windows\System32 folder.

8. Restart the computer.

Since you're using the exact copy of XP that was previously installed, the original Wpa.dbl file will be accepted, and you won't have to go through activation.

Note: The above procedure will work only if you've made no significant hardware changes.