Quote Originally Posted by drozenski View Post
Because you do not legally "own" the windows operating system. The key gives you the right to use it. Microsfot is basically leasing it to you.



Differences Between Retail, OEM, System Builder, Volume Licensing, Full or Upgrade License for Windows « My Digital Life
You don't own the license key that is printed on the sticker and that is what you are selling. It is a violation of the EULA to sell that sticker by itself and therefore illegal, regardless of what you may think. That COA is licensed to the machine it came on and cannot be transferred to any other machine. Once again, violation of the EULA. It can most definitely not be sold legally.