[qqwref]

It's not really a partition. It basically keeps a big file somewhere (for this one it's called a Virtual Disk Image; mine is 8 GB) which it uses to hold all of the data for the virtual box. Then it runs everything off that, putting all of its filesystem in that one file. But as far as Windows is concerned it's just a regular old gigantic file sitting on your computer. You could theoretically send the entire file to someone else (or another computer) and load up the VM in the same state you had it in. I imagine if you had the right tools you could even take a look at the file to see how its file system is structured or extract any information from it.

And yeah, as UNGH says, there are many different ways to get similar stuff done. I actually have cygwin too but don't like it as much.