Recently, I wanted to change the Windows XP product activation key on one of my computers; I wanted to standardize my computers so that they all use the product key from my MSDN subscription. I was pointed to a site that indicated Microsoft has posted some steps to get this done. Other sites have posted similar information. I followed all of the instructions, but I was never prompted to reactivate the installation. Everytime I tried to manually start the Product Activation Wizard, I kept getting a "product already activated" message. Ultimately, I had to rename the Wpa.dbl file, and after doing so, I was prompted to reactivate Windows XP using the new product key.
Thanks to Michael Aldridge for pointing me to these resources!