REDMOND, Wash.--Microsoft is making a change to its policies for Windows Phone 7 that will allow applications to more easily run when the screen is turned off.

Until now, applications that wanted to run when the screen was locked had to get the user's explicit permission. Under new rules announced on Friday, programs can do so without permission--provided they first demonstrate to Microsoft that they only use a reasonable amount of battery life (allowing more than six hours of use for an app playing audio and more than 120 hours for a program that does not play audio).

The move comes as the first Windows Phone 7 devices have gone on sale in Europe and Asia, with the first phones hitting the U.S. market on November 8.

The policy change is a matter of both convenience--audio apps, for example, make sense to play when the screen is off--as well as fairness. Many of Microsoft's own apps, including application downloading, e-mail syncing, and Zune playback and downloads are all allowed to happen in the background.

"This is an example of us continuing to listen to customers," Microsoft's Charlie Kindel said in an interview at Microsoft's Professional Developer Conference here. "We think it is a much better experience."

Some developers have complained that Microsoft allows only certain tasks to run in the background and also that its applications do things that third-party programs cannot. Background music playing is one such feature, while another is direct control of the camera for tasks beyond basic image capture. Microsoft has allowed, for example, hardware makers like LG to do an augmented reality app, but that is not something an ordinary developer can do using the available tools.

Kindel reiterated that Microsoft plans to add more controls and programming interfaces over time but has no plans to allow developers to write native applications. Third-party applications have to be written for either Silverlight or XNA development environments.