A Quick note,
Except with regards to WindowsXP, neither the media you use to install, nor the CDkey/product code matters AT ALL.
The only thing that microsoft really cares about is the number of licenses you own.
Naturally with XP and it's product activation BS, it's a little different.
A Computer company acn use one of their own product codes to install an OS - the only thing that really matters is that the customer is provided with a license, a copy of windows (or a proprietry restore CD, like with a Compaq), and their own product code in case a re-installation is ever needed.
A prime example of this, is that some laptops are shipped with a Restore CD that gives you a one-time-choice of win2000 or win98.
They give you the keys for both, so you can decide to use either - but legally you cant change your mind down the road.
Now if a key was really as important as a license, that'd mean those laptops give the customer 2 licenses for the price of 1... which is not the case.
Also, a Win98 license allows you to install a copy of win95 instead, if you so wish. I BELIEVE, though im not sure 100% about this one, that the WinME license covers 95 AND 98 - but definately 95.
Now as a 98 key wont work with 95, that's another indication of how unimportant product codes really are.
Your chances of Microsoft going "yes, this man is correct" are prety slim, but if it comes down to an audit, if you abide by the above, you're safe as houses.
BTW; not speaking for my company either...