If you want to run Windows 7 in a VM using a Linux box, I would recommend using KVM (http://www.linux-kvm.org/page/Main_Page) instead of using VirtualBox. I initially tried using Virtualbox to run Windows on Linux... but it had a hard time running multiple applications (multiple Visual Studio's, etc...). When I switched to using KVM, it was light years faster. All performance/reliability issues disappeared instantly. Never going back. So I now have all the goodness of Linux with an almost bare metal Windows VM.