this should work if you have the same versions.

Step1
Click "Start" and go to "Run." Enter the following string:

%systemroot%\system32\oobe\msoobe.exe /a
Step2
Click "Yes, I want to telephone a customer service representative to activate Windows" and then click "Next."
Step3
Click "Change Product Key."
Step4
You will now be able to enter the valid serial number for your Windows XP.
Step5
Press "Update" and close the window.
Step6
Now restart your computer. Your version of Windows XP should now be updated with the new serial number.