You struck M$ on a very good day for you anyway as even any upgrades that I perform that require reactivation require me to ring M$ negotate their computerised service just to speak to a human and then explain exactly what I've done then if they aresatified they give me an activation key. I do have a slight advantage being a M$ Partner but they are really on the ball about this one and insist that I not only activate the OS but any programs eg Office XP as well.
The M$ computer tells me that activation should take about 5 minutes but I enveribly spend upwards of .5 of an hour just to get the key which they insist that I type in as they give it to me just to make sure that the thing actually works.
But just to be on the safe side ifit was an OEM version then stick the CAO on the box and if it was a retail version then claim ingorance as to what exactly happened if you have the proper number of licenced copies around then they won't be too concerned but in Australia M$ have proscuted many vendors for cloning the HDD then selling OEM versions of XP with each computer as the product key doesn't match the one in the computer. They almost always win these court actions and the ones that they don't win are settled out of court to save money. It's just another way of M$ making it more diffictual for the system builder. But on a side note if you are a big business then you don't have to go through the activation process as the Volume Licencing copies of XP don't require thisprocess, you just get 1 CD with permission to install it on X number of computers the X being the number of licences that you have bought.