The bottom line
There are differences between Retail and OEM - it's not just one comes in fancy packaging and the other doesn't.
There can also be quite a difference in price between Retail and OEM and it is unfortunate that people look at price before they look at the actual license agreement and see just how flexiable the Retail license is (or rather how inflexible the OEM one is).
Let us just assume that the Retail license is twice the price of the OEM (it isn't, it's actually around 50% more expensive).
As soon as you replace your motherboard once buy a new OEM license you are breaking even - you've purchased two OEM licenses, had you purchased Retail in the first place you could have simply transfered it.
Replace your motherboard a second time during the life of the OS and have to buy a third OEM license and you're now out of pocket.
Once you have finished with your Retail version of the OS, so long as you haven't used it with an Upgrade you can resell it, you cannot resell an OEM license.
There is a good chance that you will be told (more than once) that there is no problem reactivating an OEM version of the OS even if you have upgraded your motherboard.
This takes us back to the "legally" and "physically" statement at the beginning of this guide.
From the license point of view you cannot do it, physically however you can probably get away with it - it may well activate online without a problem, if you phone up you can just lie and say that it's a replacement motherboard.
These same people will tell you that if Microsoft activate the OS online or do so over the phone then it must be legal as the person you spoke to is representing Microsoft.
Again this is incorrect because in all cases when you tell them 100% truth you will be told that you need to purchase a new license.
Phone up and tell them that it's not an upgrade, you're simply doing a warranty replacement and they will almost certainly give you the reactivation code.
However, and this is the part people don't like to see or hear:
You will be no more license legal than somebody who had illegally downloaded a warez copy of the OS
So if you've got any intention of breaking the EULA, by reactivating an OEM copy after an upgrade then it would make more sense stealing the software in the first place - don't pay for it and you'll be just as legal.
If however you've made a decision to get legal, to buy Windows (remember for what it is it's really not that expensive - you use it every day) then buy the right license for you.
There is a massive difference between what can be done legally and what can be done physically - it's just a lot of people think they are the same thing......they aren't.
