Thanks to VirtualBox, the free virtualization software from Oracle, you can use different operating systems (Windows, Linux, ...) on your computer at the same time.
Supported guest Operating Systems (the Operating Systems that you can execute into the virtual machine):
Windows: 8.1, 8, 7, Vista, XP, 98, 2012, 2008, 2003, 2000, NT
Linux: Ubuntu 5.10, 6.06, 7.04-12.10; Debian 3.1, 4.0, 5.0, 6.0; Suse 9, 10; OpenSuse 10.2, 10.3, 11.0-11.3; Mandriva 2008, 2009.0, 2009.1; Mandrake 9.2, 10.1; Fedora 1, 4, 5, 6, 7-15; RHEL/OEL/CentOS 3, 4, 5; Red Hat Linux 7, 9; Xandros 4; ArchLinux
Solaris: 10 5.08 and later, 11; OpenSolaris 2008.05 and later
Mac OS X: Server Leopard, Snow Leopard
Unix: FreeBSD; PC-BSD 7.1.1, 8.1, 9.0 and later; OpenBSD
Others: DOS; OS/2; QNX Neutrino; Haiku; Syllable; ReactOS; SkyOS.