Virtualization Software. The Best Virtualization Software category is new to the Readers' Choice awards this year. Virtualization software uses virtual machine (VM) technology, which enables multiple OSs to run concurrently on one server or one client. The first winner of the Best Virtualization Software award is Microsoft Virtual Server 2005. Virtual Server 2005 helps increase operational efficiency in software testing and development, legacy application rehosting, and server consolidation scenarios.