Microsoft is once again causing problems for its customers, closing down support for tracks purchased under its failed 'PlaysForSure' campaign.

The company is warning customers - who paid good money for music using the now defunct MSN Music service - that it will no longer supply authorisation keys for the tracks they bought.

What this means is that after 31 August, music fans who want to shift their sounds from one computer to another will be blocked from doing so. It also means that once all five Windows PCs a user can have authorised for music playback have failed, they will lose their music.

The company warns its customers: "You will need to obtain a license key for each of your songs downloaded from MSN Music on any new computer, and you must do so before 31 August, 2008. If you attempt to transfer your songs to additional computers after August 31, 2008, those songs will not successfully play."

Microsoft's customer-friendly warning that it is about to effectively destroy user's music libraries comes days after the company failed to get a lawsuit complaining that its 'Vista Capable' marketing campaign was misleading thrown out of court.

Critics observe that the move represents the biggest example yet of the dangers of DRM - what happens to customer's music collections when a company ceases to support DRM?

In this case, they lose their music.