I recently bought a Mac Book Pro and repartitioned the drive to have three main partitions: one for Mountain Lion, one for Windows 7 and one for sharing data between the two. Through a lot of research, hair pulling and a little bit of magic, I was successfully able to get the computer to dual boot into either OS X or Windows and have each OS access the data partition.
The next step was to virtualize the Windows partion so that I could run it in VirtualBox while booted into OS X. Using the createrawvmdk option in VBoxManage I created a raw disk and specified the Windows and the data partitions. This led to a "VERR_RESOURCE_BUSY" error when starting the VM. After reading through the VirtualBox manual (http://www.virtualbox.org/manual/ch09.html#rawdisk) I found out that volumes must be unmounted on OS X before they can be used in the VM. If I unmount the volume from OS X I am able to start the VM and access the partition as desired, however this seems to undermine my intentions.
Are there any options to make this data partition available to both OS X and Windows at the same time? Ultimately, I would like Windows to see the data on data partition in the same manner (i.e. as the D: drive), regardless of whether I am booted into it natively or through VirtualBox.