I tweeted this earlier today, but decided to blog it too. Here is an excellent screen cast on running IE (well, Windows too) in VirtualBox. Since the vhd’s are from Windows, and for the express purpose of cross browser testing, I’m assuming everything is above board.
A couple of notes: The screen cast is for OS X, but everything worked fine on Ubuntu. I just did a couple of things differently. I used wine to extract the exe’s, rather then 7zip. I also received a funky error from VirtualBox when I tried to run the image, but the error description told me exactly how to fix it.
The last thing I’ll note is that many comenters had problems w/ VirtualBox 2.1.0, so stick to 2.0.6.