Virtualization is a technology, which drastically reduces the time required for setting up each machine, installing a build and testing it from days to few minutes. Virtual infrastructure software facilitates running multiple operating systems and application simultaneously on a single Intel based PC. Some of the features of VMware virtual infrastructure software are:

• Running multiple operating systems concurrently on the same computer, including multiple versions of Microsoft Windows, Linux, NetWare and DOS
• Creating libraries of virtual machines with standard test environments and tools for each OS and network configuration
• Consolidating multiple virtual test machines onto a single physical platform
• Automating tests sequences, including the ones that require system restart

Reference:
>> Accelerate Application Development, Testing, and Deployment with VMware Software
>> VMWare