There was an update, Windows Genuine Advantage, that was not part of the original XP installers that did the nagging about you using a shady key IIRC. The trick

There was an update, Windows Genuine Advantage, that was not part of the original XP installers that did the nagging about you using a shady key IIRC. The trick was to not install it, which was easy enough since you had total control of updates back then.