VMware continues to push its virtualization technology for Apple systems, using the Macworld Conference & Expo this week to show off the software that lets users run Windows, Linux, NetWare and Solaris alongside the Mac OS X operating system on a single Intel-based desktop.

VMware formally introduced the software, code-named Fusion, in August at the Apple Worldwide Developers Conference. More than 70,000 people have registered to download the software since the public beta was made freely available in December, VMware executives say.

VMware Fusion is expected to be generally available by this summer, when pricing also will be announced.

VMware leads the x86 server virtualization market, but has not had an offering for Apple computers because of their use of IBM’s PowerPC chips. Last year, however, Apple made the switch to the Intel chipset for its systems, opening the door for VMware to bring its virtualization technology to Mac users.

Typically, users needing both Mac and PC applications have to run separate physical systems, but VMware’s Fusion removes that necessity. Fusion enables users to run traditional PC applications and OS X applications simultaneously and share data between virtual machines.

In addition, VMware’s virtual SMP capabilities mean that users running Macs with dual-core processors can allocate multiple CPUs to various virtual machines in order to boost performance. Other features in Fusion include the ability to access physical devices from any virtual machine even if those devices don’t have drivers for OS X, and the ability to support VMware’s virtual appliances, pre-configured virtual machines that include an application and an operating system and span everything from security to load balancing to network management.

VMware Fusion will compete with similar offerings from companies such as Parallels, which was the first to bring x86 virtualization capabilities to Macs. Parallels recently released a third beta of its Parallels Desktop for Mac. The update adds USB 2.0 support; better support for Boot Camp, a new feature in Mac OS X that enables Windows XP to run on Macs; and the ability to launch Windows applications directly from Mac OS X.