VirtualBox is a family of x86 virtualization products for enterprise as well as home use. Not only is VirtualBox an extremely feature rich, high performance product for enterprise customers, it is also the only professional solution that is freely available as Open Source Software under the terms of the GNU General Public License (GPL).
VirtualBox runs on Mac OS X, Windows, and Linux and supports a large number of guest operating systems including but not limited to Windows, DOS or Windows 3.x, Linux (2.4 and 2.6), and OpenBSD.
What's new in this version:
Version 4.2.6 has fixed Guest Additions startup on Windows 2000 guests and auto-logon installation for Windows 8.