About creating virtual hard disk images

Virtual machines running in Microsoft Virtual PC use a virtual hard disk image instead of a physical hard disk to store information. When an operating system is installed in a virtual hard disk image, that virtual hard disk image becomes a virtual machine. Otherwise, it remains an empty virtual hard disk image that can be used for extra storage for an existing virtual machine.

You can create an empty virtual hard disk image by using the Virtual Disk Assistant. The virtual hard disk image is saved on the Macintosh as a file with a .vhdp file name extension. The virtual hard disk image that you create must be attached to an existing virtual machine as a secondary virtual hard disk image in order to store data on it.

There are two types of empty virtual hard disk images that you can create:

A dynamically expanding virtual hard disk image consumes only a minimal amount of space at the time you create it. As you add more data, it expands to the maximum capacity that you specify. This is the default setting.
A fixed-size virtual hard disk image consumes the entire disk space from the time that you create the disk.

To use an empty virtual hard disk as extra storage, you must first assign it a hard disk drive in Virtual PC. For more information see Specify a virtual hard disk image.

For more information about dynamically expanding and fixed-size disk images, see About reclaiming free disk space.

See also

About creating virtual machines