Motorola, the world’s second-largest maker of mobile phones, will begin selling mobile phones loaded with Microsoft’s music software in a decision that signals a victory for Microsoft over its arch-rival Apple Computer.

Motorola said on Monday at the 3GSM congress in Barcelona that it would continue selling models with Apple’s competing iTunes  Motorola phones with Microsoft’s Windows Media format will go on sale in the second half of 2006.

Microsoft wants to replicate its success with PC software in the digital music arena, but has been upstaged by Apple. Microsoft is counting on newer, high-capacity mobile phones becoming the music player of choice.

However, Apple dominates portable music device sales with its iPod, and digital music sales with its iTunes online shop.

Motorola’s thin Razr handsets have boosted its profits and market share worldwide since their debut in late 2004. But last year’s launch of the Rokr, with Apple’s iTunes, received widespread criticism. The phone, and two other models launched since, only store about 100 songs, which cannot be downloaded directly from a mobile connection.

Apple was thought to have wanted the phones to have limited functionality to preserve iPod sales, while some analysts have speculated that it plans its own music-capable mobile phone.

Mobile network operators are keen to make returns on their investments in 3G licences and to offset slowing voice revenue through content sales, although they face competition from third-party content providers.

Motorola said it introduced handsets with Microsoft’s media support in response to demand from network operators, and that together with Microsoft it would sell handsets tailored to music download services from individual network operators.

In a further boost to its mobile data aspirations, Microsoft said it last week bought Motionbridge, a French company that develops search software for mobile phone users.