Assuming that I need both operating systems running at the same time with different GUI applications, what would be the most efficient way to do this?
Should I run Windows with a Linux virtual machine, Linux with a Windows virtual machine or follow a totally different approach?
EDIT:
I often use Microsoft Office and Adobe Acrobat Pro for documentation and develop Ruby on Rails with Emacs on Linux. On Linux I use many tools on an irregular basis, like burning tools, partitioning tools etc as they are good (enough) and free.
Best Answer
It would certainly depend on what *nix applications you are referring to. The majority of open source software can easily exist in a Windows environment. Short story, you may not need to run a full stack of Linux to get the outcome you are desiring. If you mention the applications you need to run on the Linux side, most people on here will be able to help you better.
From a purely multiple OS view though, I personally would run Windows inside Virtualbox while having Linux as the resident OS. That of course is my preference though. We would need to know what your primary choice of OS is before we can make the call on what is the best route.
Info added after OP answered the intended use of the environment:
You can run Emacs on Windows http://www.gnu.org/software/emacs/. As for burning and partitioning, since they are relatively simple processes I would strongly urge you to install Linux on a USB flash drive or small external HDD and make it a persistent environment.
See here: http://www.pendrivelinux.com/
And here: https://wiki.ubuntu.com/LiveUsbPendrivePersistent
Going this route you keep your Windows environment (and Ruby dev) having direct access to the hardware with no abstraction layer involved. When you need to use the open source tools you mention simply fire up Linux from the USB drive and do what you need to. No virtualizing necessary in my opinion. But again, that is my opinion. I'm sure others will give you additional course of action to look into as well.
If you need further help with the above, let us know.