Microsoft plans to make those announcements and others related to the Marketplace on Tuesday at the CTIA conference in Las Vegas.

Some of the features of the Marketplace match those of existing mobile application stores from Apple and Google, but Microsoft -- and any other company that launches a new mobile app store -- will have to add exciting capabilities in order to match the popularity of the iPhone's App Store.

Microsoft plans to announce that people who buy an application from the Marketplace will have 24 hours to return the application for a full refund. The setup is similar to one adopted by Google when it launched its Android store last year, but different from Apple, which doesn't allow returns of iPhone apps. If a user returns an application, Microsoft will refund its 30 percent share of the sales price and the developer will return its 70 percent share.

Marketplace users will also have more options on how to pay for applications than do users of the competitive stores, said Aaron Woodman, director of consumer product management for mobile communications at Microsoft. Windows Mobile 6.5 users will be able to pay with a credit card or put the purchase on their mobile service bill. iPhone users pay for apps through Apple's iTunes content platform, and Android phone users can only pay for applications through the fledgling Google Checkout payment service, a limitation that some developers blame for slow sales.

Microsoft will also let mobile operators create stores within the Marketplace, Woodman said. The operator stores will appear among categories such as games and productivity applications in the store.