Due to the fact that you have a vmdk, but are talking about VirtualBox, it must be assumed that the virtual disk was created by one of VMware's products, then imported into VirtualBox. VirtualBox has been able to read VMware's vmdk format since, at least, version 1.6.2 (see: changlog), including the rawdisk/partition formats.
Do you have more than one partition on this machine? Could the VMware XinXP-pt.vmdk be pointing to an actual physical partition on the HDD?
For example, there is documentation about how to set up raw virtual disks in WMware Workstation:
I'd run gparted, parted, or fdisk to look for additional partitions on the host drive. Also, it might help you post the contents of the vmdk file.