Yesterday I installed XP pro on my laptop, on a whim, just because, really. So, I pulled out my old xp install cd, but, alas, I couldn't find the right serial number, so, I just got one off the internet, and was like, I'll change it later, and just won't use windows update.
So, it was chugging along, and, I was like, I should probably update, just to get sp3, and remember that the serial number is on the bottom of the laptop (duh). I googled around for a way to change it. Well, the disk I had was a corp disk from my work, I totally forgot, so, the utilities would not let me change it to my OEM cd key. I figured WGA had to have something to tell me about this. And you guys did, after clicking around through everything, WGA asked for my legitimate CD key, and then said that I could just download this application and it would change the key for me. I did, and 5 mins later, I'm now legitimate, and downloading SP3 as we speak 
I was suprised at how put together WGA was, and how unaccusing it was as well.
Good Job.
-Erik