Amazon Web Services Thursday launched a public beta of its cloud-computing service running Windows Server and SQL Server, marking the first time developers and businesses can use the Amazon Elastic Compute Cloud (EC2) to build and host applications on Microsoft's software.

AWS, a subsidiary of Amazon.com, also said Thursday that EC2 has emerged from beta and now can offer SLAs (service-level agreements) to customers. The SLA guarantees 99.95 percent availability within a geographic region over a 365-day period, or customers are eligible to receive service credits back, according to AWS.

Customers can sign up for EC2 online.

EC2 is part of Amazon's AWS suite of cloud-computing infrastructure services. With EC2, developers and businesses can host and run their applications on Amazon servers, increasing or reducing capacity as needs change and paying only for what capacity they use on a pay-as-you-go basis.

Pricing for using Windows Server with Amazon EC2 begins at US$0.125 per compute hour, according to AWS.

Even as developers can now use Microsoft software on EC2, Microsoft is developing its own cloud-computing infrastructure that could compete with EC2. Speaking in London earlier this month, Microsoft CEO Steve Ballmer said Microsoft would unveil a cloud OS tentatively called "Windows Cloud" in about four weeks' time, which would mean early November.

More details about Microsoft's strategy could emerge next week at its Professional Developers Conference in Los Angeles or the following week at the Windows Hardware Engineering Conference in the same city.