Announcing a major shake-up i its management structure, software giant Microsoft Corp today said that its entertainment and devices unit president, Robbie Bach, would retire soon -- strengthening CEO Steve Ballmer's hold over the company.

The company said in a statement that besides Bach, who is expected to retire this fall, Microsoft veteran J Allard would also be leaving soon.

However, Bach would not be replaced. Instead, the heads of the mobile communications business and the interactive entertainment business would report directly to Ballmer, with effect from July 1.

Senior vice president Don Mattrick would continue to run the Xbox business while senior vice president Andy Lees heads the mobile unit.

J Allard, senior vice-president of design and development for entertainment and devices (E&D) division, would take up an official role as advisor to Ballmer and his team. He had served Microsoft for 19 years, the statement added.

Commenting on Bach's departure, Ballmer said,"For the past 22 years, Robbie has personified creativity, innovation and drive. With this spirit, he has passionately devoted his efforts towards making Microsoft successful in interactive entertainment and mobility."

Bach, for his part, said that he plans to spend more time with his family and indulge in non-profit activities.

Microsoft also stated that David Treadwell, corporate vice-president of Live Platform Services, would take up a new position as head of the core technology organisation for the Interactive Entertainment Business -- reporting to Mattrick.

Among other changes, Antoine Leblond, senior vice-president in the Office Productivity Applications Group, would take over as senior vice president for the Windows Web Services team.

Kurt DelBene, senior vice-president in the Office Business Productivity Group, would take up all engineering responsibilities for the section.