Microsoft Corp. is unveiling copyright protection software to allow rented songs or movies to be used on portable players, cellular phones and other devices. The company's latest "digital rights management" software, code-named Janus, was released Monday. It will give songs and videos purchased through subscription services a sort of digital expiration date that works even when the data is transferred from a computer. The technology also protects the content against piracy.

The goal is to make it easier for companies who want customers to rent songs or videos, rather than own them, to also let those users play back the content on portable players. For example, with the new technology a user could rent several movies for a long trip, download them onto a portable player and then watch the movies until the rental expires a month later. A user also could rent songs for a set period and play them back on a portable player. "At the moment the current subscription models that are out there are so hobbled by the fact that they cannot be taken away from the computer," Microsoft spokesman Jason Reindorp said.