This is kind of a feature request, but I'm not sure where to post it. You can use the Parallels Image Tool to expand a hard disk image, but you then still have to change the partition size within your guest OS using other tools. It would be great if, at least in Windows (since this is a very common guest OS), this were built in, maybe as an additional component of the Parallels Tools, so the user would no longer have to use other tools like Partition Magic or Acronis Disk Director.