Or Linux system. Or another Windows.
Latest release has experimental support of OpenGL acceleration which is real nice. Now more jealousy to Mac OS X virtualization platform choice. I haven’t tested it personally (and most likely will wait for DirectX 9 support first).
(In case you’re wondering why “solaris/nvidia”, my reasoning is: both VirtualBox and Solaris are “owned” by Sun; and that nvidia seems to be the best supported vga on Solaris. CMIIW 🙂 )