The good news is that the license allows installation on up to three machines and (over time) you can transfer the license to new systems.
From the license: "You may install one copy of the software on three licensed devices in your household for use by people who reside there. ... During activation, the software will send information about the software and the device to Microsoft. ... You may reassign the license to a different device any number of times, but not more than one time every 90 days."
Read More >>