Microsoft has finally launched its Azure cloud computing platform, more than a year after it was originally announced. The software, which promises an operating system in the cloud, will be a "community technical preview" until the end of the year, and then go live for paying customers on 1 January.

The idea behind the system, which competes with Amazon's elastic computing service, is that developers will be able to build web apps on the service, and consumers will be able to store data that'll be accessible from any web connection. The first month of the service will be free, and billing will start in February, said Microsoft's Ray Ozzie.

He added: "Customers want choice and flexibility in how they develop and deploy applications. We're moving into an era of solutions that are experienced by users across PCs, phones and the Web, and that are delivered from datacenters we refer to as private clouds and public clouds".

Azure will be priced from $0.12 to $0.96 per service hour depending on how much power you need. All virtual machines come with 1.75Gb of memory.