[VirtualBox 4.0.4] adds some GUI enhancements to the virtualization software. Be sure to also install the “VirtualBox 4.0.4 Oracle VM VirtualBox Extension Pack” to support USB 2.0.
I had some initial issues running a guest of Windows XP on Windows-7. The same guest worked on Linux and MacOS. It turned out to be necessary to disable the 3d acceleration in the VM settings to avoid a crash during start-up.
To install 3d-acceleration on a Windows-XP guest, you have to boot into safe-mode.