[color=66ff00]Well I'm thinking about it in this way:
Most people are on 56K, thus most people don't generally download what amounts to pretty hefty downloads. The result is that MS doesn't know who's upgraded and to what level for a large proportion of 'doze users.
If they give out these free CD's they effectively get the name and address of Joe user, they can then verify if Joe user got a legit copy of windows (if it's XP and it's registered), they know that he's running the service pack that's been distributed on the disk he ordered (and probably media player, MSN messenger, IE6 and whatnot) and they can no doubt use this info to get more accurate marketing data.
I'd say that amounts to keeping tabs.
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