When w9x was pop, you could just delete the product key from the registry and shut it down. It would then ask for the key upon first start.
I've done few syspreps on w2k computers. But can't remember if it did remove the key or not. My guess would be it did, and since w2k is pretty much same as wxp, I'd think that yes.
But you obviously have a lot of tools with you, so you can easily test it out

-M