Microsoft getting paid twice for windows on the same PC ?

From PC World:

Microsoft launched a program to help ensure that PC refurbishers and OEMs reselling used PCs to businesses are installing legitimate copies of Windows on them.

Windows licenses are tied to the computer for which they are acquired. PC refurbishers can reinstall Windows on a rehabbed PC if they have the correct proof-of-purchase documentation -- called a Certificate of Authenticity -- and the original OS image software necessary to return the PC to its original state. However, it's often difficult to have both of these items handy for old PCs, and companies reselling used PCs will sell them without an OS installed. This leaves the PCs open for people who buy them to install Linux or a pirated version of Windows.

These computers were shipped with a copy of windows on them the first time, can anyone explain to me why we need to pay Microsoft twice for the same copy of windows ?  This is clearly another example of Microsoft exploiting it's monopoly powers to pressure people into not only running it's software, but paying twice for the privilege.

They are terrifed that these computers might end up with an OS other than Windows on them.

What a joke......