I have Windows 7 and Linux Mint installed on two separate partitions, and I'd like to access a virtual machine (.vdi) from either of the two partitions. Is it possible for Virtualbox to access a virtual machine that is stored on a separate hard disk partition (e. g., booting a virtual machine that is saved on Windows while running Linux as the host OS)?
Yes it is. As long as both hosts can see the file, just create a virtual machine, and attach he existing hard drive file. For this set up, out the file on the Windows side