How do I run VirtualBox on a Macbook? Is it possible, or do I need Parallels? I want to run Windows7 on my 15" macbook pro along with the original OSX Mountain Lion.
Presently, VirtualBox runs on Windows, Linux, Macintosh, and Solaris hosts and supports a large number of guest operating systems including but not limited to Windows (NT 4.0, 2000, XP, Server 2003, Vista, Windows 7), DOS/Windows 3.x, Linux (2.4 and 2.6), Solaris and OpenSolaris, OS/2, and OpenBSD.
Assuming you have an Intel based Mac, yes it is possible and simple.
Just download Virtualbox and install. You can then fire it up and run whatever virtualized OS you desire.