Steve Ballmer hasn't quite ridden off into the sunset yet. The Microsoft CEO has agreed a $7bn acquisition of Nokia's mobile division, transferring hardware licenses, patents and 32,000 employees.

Nokia's flagship smartphone Lumia already runs on Microsoft Windows operating system.

"As long as we were on a model with two different companies...there was always some kind of a boundary along which it was hard to innovate from a hardware/software perspective," Ballmer said in an interview.

"We've done a lot of great work in the two-and-a-half years that we've been in partnership with Nokia, going literally from no phones to 7.4 million smart Windows phones in the last quarter that was reported."

The Finnish company are still the second-largest phone manufacturer behind Samsung, selling 60 million units in the last quarter; but remain well behind Apple and HTC in the smartphone battle, representing just 3% of the market.



Nokia shares spiked 45% upon news of the deal.

"We know, as we scale, we need to invest behind this business," said  Ballmer. "It simplifies the business decision making and thinking having the economics be more unified."