Virtual hard disk created by Parallels Desktop virtualization software; stores the data for a virtual machine's hard drive (you can think of it containing the Windows C:\ drive for Windows VMs); used for loading the VM's files when the VM is started.

HDD files are stored within .PVM virtual machine files. To locate your HDD file, right-click the PVM file and choose "Show Package Contents." The folder that is opened has an HDD file with the same filename prefix as the PVM file. To recover files within an HDD file manually, you first mount HDD files manually with Parallels Mounter, a program included with Parallels Desktop (located in /Library/Parallels/). Next, right-click the HDD file and choose Open With → Parallels Mounter.app. NOTE: Older versions of HDD files from Parallels Desktop version 2 can be opened by Oracle VM VirtualBox.