If you are Apple Programmer or Developer then you must aware of this because it make very difficult work on windows with .dmg extenstions as compare to Mac OS X,Officially these kind a file are unsupported on Windows,This Guide is quite useful to know what dmg file is and how to open it.
What Are DMG Files
Many people thinks that if files appear as unknown files then they are viruses or malicious files, but this is not true at least on this case. DMG files are Mac OSX Disk Image files. They are essentially disk images like ISO,RAR files, their Windows based computer.
These disk images generally contain the program installation files for Apple applications,also be used to hold compressed files. Since they are belongs to Mac installation files, you cannot install or run these kind programs on Windows. You will need to download the Windows version of the program with the EXE extension.
There are basically one way to open or access the .dmg file is to use third party software like 7zip and DMG extractor
Using DMG Extractor DMG extractor is a free version software which is great for unzipping DMG files, but if your file is bigger than 4GB, you will need the professional version.The paid version also offers encrypted DMG file extraction capabilities.
Open a .dmg file and exctract to any location which you want
7-Zip is a powerful compression tool that is distributed freely to users. Its installation file is completely free If you do not have 7-zip installed on your computer, you can Download and install it on your machine.
Select a .dmg file and extract to any location which you want ,The program will begin extraction which will go as fast as your computer can manage