Microsoft announced the Windows Phone 7 OS for handheld devices on Monday, taking a step forward in the company's efforts to strengthen its position in the still growing smartphone market. CEO Steve Ballmer unveiled the first phones to run the OS, and named the network operators that will distribute them.

"We wanted the Windows Phone to be delightful across a range of hardware devices, through a range of scenarios, and a [range] of different software experiences," Ballmer said.

Microsoft wanted to make Phone 7 "always delightful" and "wonderfully mine," he said, emphasising the way that users will be able to customise the user interface. "Everyone should look at the phone and represent themselves on the device," he said. Sixty mobile operators will be offering it in 30 countries, he said.

In Europe, Orange plans to launch three Windows Phone 7 devices. The HTC 7 Mozart, which will be exclusive to Orange, will be available in France, the UK, Spain, Poland, Switzerland, Romania, Portugal and Austria. The Samsung Omnia will be available in France, the UK and Switzerland, with the LG Optimus 7 available in France about six weeks ahead of other operators, Microsoft said.

Windows Phone 7 is a totally revamped operating system, designed by Microsoft to better compete with new rivals in the mobile market such as Apple and Google. The operating system was a long time in the making. Apple's iPhone launched in early 2007 and by the end of that first year it had outsold all Windows Mobile devices in the US, according to researchers at Canalys. Microsoft released the stopgap Windows Mobile 6.5 in 2009, but it failed to reverse Microsoft's slide in the mobile market.

While Microsoft is in an underdog position competing against market leaders Research In Motion, Apple and Google, it offers notable benefits. Enterprise IT managers are likely to gravitate toward Windows Phone 7 devices because they'll work well with Exchange and other widely used enterprise software from Microsoft.

In addition, Microsoft has said that it is determined to succeed in the mobile market. With its deep pockets, it is likely to continue to invest in improving the standing of Windows Phone 7 in the mobile market.

Finally, Microsoft has recently been pointing out that its broad patent position protects handset makers who choose to build phones using Windows Phone 7. This is becoming an important issue, as Android faces legal threats from Oracle, Microsoft and Apple.

IDC in a recent study placed the market share of Windows mobile operating systems on devices like smartphones at 6.8 percent, behind Symbian, which took the top spot, Research in Motion's Blackberry OS, Google's Android and Apple's iOS. IDC expects upcoming Windows mobile operating systems to help Microsoft regain market share, reaching 9.8 percent by 2014.