I'm pretty sure that MicroSoft brought out the new registration feature with XP. This isn't the ordinary "new product" registration that you can skip with most products; with XP, the product becomes inoperable after a short period of time if you don't register on line with MicroSoft. And, during the registration process, MS matches your product serial number with the serial numbers of some of your hardware. So, if you change, for example, your CPU, the new CPU serial number will not match and you will be on the phone with MS explaining what you did so that you can use your computer again. Rather intrusive if you ask me.
You're right about the other issues I have with XP at work; they are simply issues brought about by the methods that our IT department has decided to use. I'd really like to slap one of those folks around for having such a cocky attitude the day he installed XP in our machines. He rendered the computer nearly useless.