HFS and .DMG extensions are used in Mac OS X. Hierarchical File System A.K.A HFS is a file system for use in computer systems running Apples Mac OS. HFS was designed for use on floppy and hard disks, it can also be found on read-only media such as CD-ROMs. HFS Plus successor of HFS Standard is also called Mac OS Extended or HFS Extended. .DMG stands for Disk Image, .DMG uses a proprietary disk image format commonly found on Mac OS X. Its most common function is the distribution of software over the Internet. When opened, DMG files are "mounted" as a drive within the Finder. DMG files can be easily created (with or without encryption) using Disk Utility included in OS X. In Windows, most dmg images can be opened using several other programs such as Acute Systems TransMac, HFSExplorer, UltraISO or IsoBuster. If you are looking to explore or extract HFS or .DMG in Windows environment we recommend HFSExplorer. HFS Explorer is written in Java with GUI, and it supports more advanced features of dmg including AES-128 encrypted images but not UDCO images. Overall it’s a freeware.
HFSExplorer is an application that can read Mac-formatted hard disks and disk images.It can read the file systems HFS (Mac OS Standard), HFS+ (Mac OS Extended) and HFSX (Mac OS Extended with case sensitive file names).HFSExplorer allows you to browse your Mac volumes with a graphical file system browser, extract files (copy to hard disk), view detailed information about the volume and create disk images from the volume.HFSExplorer can also read most .dmg disk images created on a Mac, including zlib / bzip2 compressed images and AES-128 encrypted images. It supports the partition schemes Master Boot Record, GUID Partition Table and Apple Partition Map natively.