Theres a kernel module for it, called ndb, provided by QEMU. Thus, for it to work, you'll need to modprobe-it. Do as follows:

# rmmod ndb # just to be sure
# sudo modprobe nbd max_part=16 # particularly important

Then, run qemu-nbd to map it:

# qemu-nbd -c /dev/nbd0 /media/Arquivos/XP_System.vdi

Now, the partitions will be available under /dev/nbd0pX (where X is the partition).

For e.g.:

# mount -t ntfs -o users,umask=000 /dev/nbd0p1 /media/Arquivos/XP_System.vdi /mnt

You can also use, I don't know, fdisk, maybe:

# fdisk -l /dev/ndb0

It'll list the available partitions.

https://askubuntu.com/questions/19430/mount-a-virtualbox-drive-image-vdi