• Boot from an existing (real) hard drive
  See manual, section "Using a raw host hard disk from a guest"
  Basically, you'll create a special .vmdk file, using the command-line tools. On Windows, you do the same thing, but you use UNC paths rather than the /dev/ style descriptor. (I went right click > Properties > Tools(tab) > choose the drive > Properties > Volumes > Populate > see "Disk" field) You can use the listpartitions command to make sure it's the right one.
• Setup folder sharing
  1) install Guest Additions. 2) mount -t vboxsf <vbox-foldername> <mountpoint>