I suspect the legal reason is licensing - you've won the item, but a condition of the license given to you is that it cannot be resold.
The business reason of course, is that they don't want people profiteering from their giveaways. Think about it, every person that buys a gift version of Windows is one less customer that might have bought it from them. This is actually quite common and goes beyond Microsoft and computer software, prizes (e.g. tickets to an event) are often non-transferrable.
The business reason of course, is that they don't want people profiteering from their giveaways. Think about it, every person that buys a gift version of Windows is one less customer that might have bought it from them. This is actually quite common and goes beyond Microsoft and computer software, prizes (e.g. tickets to an event) are often non-transferrable.