Ex-Microsoft exec spills beans on Ballmer management style

In his book, Kempin writes about how Microsoft foresaw the major moves in technology in the last decade, but bungled its entry into tablets, phones and social media, ceding leadership in the technology world to Apple Inc and others.

"They missed all the opportunities they were talking about when I was still in the company. Tablets, phones...we had a tablet going, we had tablet software when Windows XP came out, it was never followed up properly," said Kempin.

He also claims the decline of PCs is partly due to Microsoft's mismanagement of hardware makers, an area that Kempin oversaw at Microsoft.

"Just think about the insult of Microsoft coming out with a tablet themselves, trying to mimic Apple, and now they are going to come out with a notebook on top of it," said Kempin, referring to Microsoft's Surface RT tablet and soon-to-be-released Surface running Windows Pro.

Several PC makers went public with their unease about Microsoft's decision to make its own computers last year.

Kempin reserves his most pointed criticism for Ballmer.

"Is he a great CEO? I don't think so. Microsoft's board is a lame duck board, has been forever. They hire people to help them administer the company, but not to lead the company. That's the problem," said Kempin.

"They need somebody maybe 35-40 years old, a younger person who understands the Facebook Inc generation and this mobile community. They don't need this guy on stage with this fierce, aggressive look, announcing the next version of Windows and thinking he can score with that."