Microsoft Corp. (MSFT) is planning to shake up its marketing unit as the company grows increasingly unhappy with the results, a move that could lead to hundreds of job cuts.

CEO Steve Ballmer doesn't think the company is getting enough return on the billions it spends annually on marketing, especially at a time when Microsoft is facing increasing threats in corporate computing from Amazon Inc. (AMZN), Google Inc. (GOOG) and Apple Inc. (AAPL), Bloomberg reported Wednesday.

Microsoft could be announcing the initial steps within the next 30 days, but the plans aren't final and are subject to change.

Chris Capossela, who took over as Microsoft's chief marketing officer last year, is reportedly leading the restructuring. According to people familiar with the matter, changes many include shifting marketing employees who have more technical skills to engineering groups and axing those who don't have needed skills or whose work is duplicated by other workers.