A ideia é interessante, mas tem um problema de acordo com esta matéria:
http://www.computerworld.com/s/article/9127980/Take_Windows_7_for_a_spin_with_VirtualBox
O Windows virtualizado rodaria lento em jogos!
"You should be aware, though, of some fundamental differences between running an operating system in a VM and running it natively. The most common problem is the inability to use the higher performance features of graphics, audio or network cards. That's because, like most virtualization software, VirtualBox provides the guest operating system with a virtual VESA-compatible graphics card, a virtual Intel ICH AC '97 audio and several virtual network cards. In short, your virtual Windows 7 can't use your high-end graphics card or what-have-you because only the host system has access to it, not the guest operating system, which must use virtual drivers instead."