Microsoft has started beta testing software that will take its Web e-mail onto the desktop.

This week, Microsoft served up the first test version of Windows Live Mail Desktop, a free Windows program that will let users manage multiple e-mail accounts. The software is designed to work with Windows Live Mail, the successor to Hotmail that is also in beta testing.

The move is a shift for the Hotmail business, which in the past, has charged users who wanted to read their mail using desktop software rather than a Web browser. Microsoft charged $20 and more for its paid service. It’s part of the company’s broader Windows Live effort and could eventually serve as a hub, not just for Windows Live Mail, but for other Microsoft Web-based services as well.

In addition to working with multiple Windows Live Mail or Hotmail accounts, the new desktop software can be used to manage POP3 or IMAP accounts, potentially even Google’s Gmail, said Brooke Richardson, a lead product manager for the Windows Live Mail group.

The current test is limited to a small group of about 100 testers.

“They are going to kick the tires for us,” Richardson said.

If all goes well, Microsoft plans to release it to several thousand testers in the coming weeks or months, with a final version before the end of the year. About 1 million people use the test version of Kahuna, the code name for the Web version of Windows Live Mail.