Back a couple years ago when Windows 7 was first rolling out, I recall some noise about all but the Super Galactic Ultimate editions being impossible to run in a virtual environment (like VMWare or, in my case, VirtualBox). This older question says "any version" but it also says "commercial license", and I don't know what that means.
I'll phrase the question this way, therefore: I'm running Linux, and I've got VirtualBox. I have no license (or even media) for Windows 7 at all. If I drive over to a retailer to buy a copy of Windows 7 with the intention of running it in VirtualBox, what version do I need to buy? I don't need any OS features other than the ability to run newer IE versions (9 and 10 etc), so things like networking limitations or server features are completely unimportant. Obviously what I'd prefer is to buy the cheapest thing I possibly can.