Take a backup of the '.hds' file in an external hard disk. Then remove the file from the Mac hard disk and check whether the virtual machine is working fine and you have all your programs and data files. If it works fine, then you can delete the '.hds' file. Else, you need to restore the file to the same location because some of the virtual machine files might be located in the '.hds' file and you need both '.hds' and '.pvm' file to start the virtual machine.