But what about this.
I owned a Laptop that has a legal XP on it. The laptop breaks. So I figure "Well, I can use the XP disk with my desktop right? Since it would still only be installed on one PC, which should be acceptable following the "One software license, one PC rule." WRONG! Tried it once, even called Microsoft and they said they couldn't let me use the license with my desktop. Bull***.
You had a moron on the phone then. Just call again and get a new rep. They're supposed to let you transfer an OEM license if the hardware was replaced due to malfunction. Although it COULD make a difference if you have some proprietary HP license or something, I've never had to deal with that.
Mind you, I've been on the same license through multiple hardware revisions. Most MS reps know and just don't care.
If it's mission-critical for you to have a transferable license, you're supposed to get a retail copy, not OEM.
I update all my drivers regularly....I just avoid connecting M$'s servers as far as possible. No stupid IE7, WMP11 or WLM downloads that require WGA checks during installation (it might still pass as BigIg said, but there's no assurance, plus the benefit from the 3 is also very minimal IMO).

The LEAST of windows updates deal with things like IE or WMP.
The important ones patch security holes, improve performance, and fix bugs.
Till you consider what the call charges are for the other side of the world........
Any MS numbers I've ever had to call have been Toll Free