VirtualBox 4.2.6.82870 Final + Extension Pack + PortableAppZ | 175MB
VirtualBox - a special program to create a memory PC virtual machines. Each virtual machine can contain an arbitrary set of virtual devices and separate the operating system. Scope of virtual machines is very wide - from performing the functions of software testing to create entire networks, which are easily scaled, load-balance and protect. VirtualBox is free, open source software.