One of the problems of DRM has really come home to roost for MSN Music users. According to Digital Music News, Microsoft have informed users in writing that music purchased through MSN Music will not be transferable after August 31st 2008 to other devices or machines. This means that MSN Music users must continue to keep their existing equipment (and working) to not lose their investment. So if after August you experience a catastrophic failure of your computer then game over, your investment is lost.
My personal view is that given you have paid for the right to have a copy of the music to play that Microsoft in this situation should carry the cost of transferring MSN Music users to their Zune infrastructure which is replacing it, or allow people to re-download the music in a DRM free format.