This is why you never really own the music you purchase when you purchase them with DRM:
Customers who have purchased music from Microsoft’s now-defunct MSN Music store are now facing a decision they never anticipated making: commit to which computers (and OS) they want to authorize forever, or give up access to the music they paid for. Why? Because Microsoft has decided that it’s done supporting the service and will be turning off the MSN Music license servers by the end of this summer.