Activation was delivered as an optional "feature" that would be installed alongside all the other Windows updates, unless you opted out of it (or it was already

Activation was delivered as an optional "feature" that would be installed alongside all the other Windows updates, unless you opted out of it (or it was already slipstreamed into the install disk). From what I remember this was pushed around the time of SP2, but if you had a launch-day install disk and reformatted your disk that often then you probably never got as far as receiving that update.