Microsoft CEO Steve Ballmer today said the overhaul of Windows is part of a larger goal to transform the whole company, making every one of its businesses optimized for new hardware form factors and cloud services.

The Windows 8 user interface is a dramatic change from Windows 7, featuring Microsoft’s Metro-style tiles and optimization for both traditional PCs and touchscreen tablets. Windows Server 8, now available in a developer preview, is also being upgraded to support the shift from local resources to cloud computing, featuring greater integration with Windows Azure. In all, Ballmer counted seven Microsoft businesses—Windows, Phone, Xbox, Azure, Office, Bing, and Dynamics—and said all of them “are moving to the cloud as their fundamental business model.”

“If Windows 8 is Windows reimagined, we’re also in the process, and Windows 8 is an important step of that, of reimagining Microsoft,” Ballmer said during the second day of keynote addresses from the BUILD developer conference.

Windows Server & Tools President Satya Nadella called the Windows Azure cloud service a core piece of the Windows platform, alongside Windows Server, and demonstrated new tools that simplify the process of building an application on Windows Server and shifting it onto Microsoft’s cloud network, where it gains greater scalability. Microsoft is also examining all of its cloud services to find aspects that are interesting to developers, Ballmer said.

“In Office 365, how do we make SharePoint a general-purpose platform you can extend through Azure?” he said. “How do we take Bing data and put it in a form that is an extensible element that can be used in your own applications?”

On that second front, Microsoft demonstrated how Bing data and many other data sources are part of Azure’s marketplace, allowing developers to build more useful applications. Even cars should benefit from Azure-powered services, bringing mapping and other tools to drivers in a heads-up display, Microsoft executives said.

Ballmer boasted that that 500,000 people already downloaded the Windows 8 developer preview released this week and that the hundreds of millions of Windows users form the biggest user base of any single operating system, but he noted that Windows Phone 7 still hasn’t achieved great popularity. While Windows 8 will be the operating system for both PCs and tablets, the phone OS is also crucial for Microsoft to reach mobile users and sell them on the Metro interface.

Nokia will lead Windows phones into new geographies, price points and form factors, Ballmer said. “You’ll see us continue investing and improving on what is really a very fine product, but still a product that’s important for us to get, if you will, fully appreciated by consumers around the world,” Ballmer said.

Ballmer also reaffirmed his commitment to both Intel and ARM chips, and said Windows will help revamp not only the mobile market but the enterprise data center as well.

“It’s not going to be Intel or ARM,” Ballmer said. “It’s going to be Intel and ARM for various usage scenarios. PCs, tablet form factors, phones, new user interfaces and input paradigms like the Kinect paradigm we brought to the Xbox platform. New highly virtualized servers and really, over time, completely reconfigured data centers where the relationship between storage and compute and networking pivots dramatically from what it is today.”

Microsoft today made the Visual Studio 11 Developer Preview available to MSDN subscribers, and it will be available to the public on Friday. The developer preview of Windows Server 8 is also now available on MSDN, with Microsoft pitching it as the operating system for the cloud.

As part of Server 8, Microsoft is upgrading the Hyper-V virtualization platform, which will feature bolstered live migration capabilities. While Windows Server already provides live migration of virtual machines, next year’s release of Windows Server 8 will allow movement of virtual hard disks from one storage device to another with no downtime—for example, from a local disk to a remote file share. Microsoft also promised the ability to move a running virtual machine without the need for any shared cluster technology or specialized hardware.

Ballmer noted that not all customers are ready to move to external cloud services, and would rather run cloud-like services within their own networks. Server 8 upgrades will help keep those internal clouds running.

“Continuous availability of services typically requires expensive hardware infrastructure, but not every IT organization can afford the necessary hardware,” Microsoft VP Bill Laing wrote in the Windows Server blog. “So, with Windows Server 8 we are delivering high availability and disaster recovery at a much better price point, using software technologies and commodity networking, storage and servers. For example, we are giving customers access to high-end storage capabilities that before required specialized hardware, such as device pooling, disk virtualization, and thin provisioning, in Windows Server 8.”