Hmm.
I disable the auto-updates, and use
http://www.autopatcher.com/It's pretty sweet, especially 'cause they've got a slip-streamer that lets you include your XP CD+SP (maybe even other updates, I'm not sure) into a new CD.
As for legal use of Windows, I bought XP Pro Full. When IT gave me a problem because I liked to change my hardware

(wouldn't stop reactivating, even though the new hardware had been activated), I got XP Corporate, slipstreamed SP2 into it, and voila! I have a (sort of) legal, non-prissy version of Windows.
BTW I have like 5 computers also, and I'd like to know, if you're using an old computer just for legacy stuff, but want XP on it just because, well, just because, are you really gonna fork over 3X the total worth of the computer for the OS?!? I liked 9x because of just that situation.
Also BTW I dual-boot Linux. Some of you fellow WinDOwS guys should try it. Mandriva Linux is good for starters, it lets you resize your WinDOwS partition and it's desktop is easy to get used to, you can download it for free or buy a disc at
www.Mandriva.com .