Simple questions: What is a disc image file (ISO, NRG, BIN)?

Have you encountered the term of disk image, or that of ISO image? You may have heard it from a tech savvy friend who has a huge library of disks (CDs, DVDs, Blu-Ray disks), but he or she doesn't appear to use any of them, at least not on a regular basis. Well, that friend of yours most likely has created disk images of all the optical disks that he or she uses more often. What are disk images and why would someone create or use disc images? Read this guide and, by the end of it, you will have the answers to these questions, and more.

What is a disk image & how can it be useful?

A disk image is a file that stores all the content and the structure of an entire disk. That disk may be an optical disk like a CD, DVD or Blu-Ray disk, a hard disk drive, a USB flash drive, a tape drive and so on. A disk image is a file that's the exact copy of a disk volume or of an entire physical disk drive. This copy retains all the properties of its source: files, folders, properties and the disk's name.

Disk images are a handy way of storing backup copies of your disks. For instance, you might have some Audio CDs which you play on a regular basis. You probably don't want them to wear out fast because you use them often. In that case, a good way to listen to them but also keep them in a pristine condition - because you will actually not use them - is to create disk images for them. The disk images can be stored on your computer and you can simply mount them when you want to listen to your music. Obviously, you can rip their contents into another format, but that's another story.

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The usefulness of creating disk images for your Audio CD s is just an example, but there are more situations in which disk images prove their worth. For instance, some software vendors choose to deliver their programs as disk images, which you can download from the Internet. A very good example of that are operating systems, which are often delivered online under the form of disk images. That's because disk images are exact replicas of physical DVD disks, and because installing an operating system usually means you have to have it on a bootable disk. If you get the operating system as a disk image, which is a single file that you can download from the Internet, you can then burn it on a CD or DVD and, finally, you can use it to boot and install the operating system.

To sum it a bit up, here are some of the most prominent benefits of using disk images:

  • Disk images are exact replicas of disk drives or disk volumes, so they faithfully preserve all details related not only to content but also to the original files and folders structure;
  • A disk image of an optical disk can be very useful when you need to create multiple copies of that disk;
  • A disk image of a hard drive that contains a Windows operating system can be used to reinstall Windows very fast;
  • A disk image of a hard disk or of an optical disk has the big advantage of portability. Being a single file it is very easy to send it online to others or store it on an external hard disk drive, for instance.

The most common file formats for disk images

As we know by now, a disk image is a file stored on your disk. Like any file, it must bear a name and an extension. In other words, a file must have a file format. The most common disk image file format today is " .ISO " , but there are many other types of file formats that can be used. Here are some of them:

  • ".NRG" (Nero CD/DVD Image File) - are CD or DVD disk images created with the Nero disc authoring software.

  • ".BIN" & ".CUE" (Cue Sheet File) - are CD or DVD disk images split into two different files. One of them is a ".BIN" file that is a binary file that's an exact copy of the disk. The complementary ".CUE" file contains the details on how the data is structured on the original disk.

  • ".MDF" & ".MDS" (Media disk Image File & Media Descriptor File) - the CD or DVD image is stored inside the ".MDF" file, while the header and track information are stored in the ".MDS" file.

If you'd like to know more about all the disk image file types known to man :), check this web page: Disk Image Files.

How do you create disk images in Windows?

In order to create a disk image, you need to use a software application that knows h ow to do this. Unfortunately, Windows itself doesn't know how to create disk images and the only way to do that is to use a third party program. There are many such programs available on the Internet and most of them focus on either creating disk images of CDs, DVDs or Blu-ray disks, or on creating disk images of hard drives of all kinds.

We've covered some scenarios related to creating disk images for optical disks, in these two tutorials:

How do you mount disk images in Windows?

Windows 8.1 and Windows 10 know by default how to work with the most common file format for disk images: ISO images. I f you want to use a disk image as a virtual CD/DVD or Blu-ray disk in Windows, and if the disk image is an ISO image, then you can simply mount it. When a disk image is mounted, it will look and work the same as if it were a physical disk loaded into your optical unit. To find out how, we recommend you to follow the steps described in this guide: How to mount or unmount ISO images in File Explorer.

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If you're still using Windows 7 or if you need to work with disk images that use other, more exotic file formats, like.NRG,.BIN &.CUE or.MDF &.MDS images, then you'll have to install a third party tool.

Here are a couple of suggestions from us :

  • If you're using Windows 7, Windows Vista or Windows XP and you only need to mount ISO images, then we recommend you use Microsoft's simple and free utility Virtual CD-ROM Control Panel.
  • If you use various other types of disk images, consider Daemon Tools Lite. It works in every Windows version since Windows 98 onwards, it's free, and it also supports many file formats for disk images: B5T, B6T, BWT, CCD, CDI, APE, FLAC, CUE, ISO, ISZ, MDS, MDX, NRG, VMDK, VHD, TC. Take care though, when installing it, because it tries to install some adware that changes your browser's homepage and default search engine.
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How do you burn ISO disk images in Windows?

If you have an ISO or an IMG disk image and you want to burn it to a physical CD/DVD or Blu-ray optical disk, then this guide will provide you with the steps on how to do that in Windows, without using any third party tools: How to burn disk images (ISO & IMG) in Windows.

In case you have to mount, burn or work with disk images other than ISO images, or if you're still using Windows 7, than you will have to use to third party tools.


Now you know what disk images are, why they are useful, how to mount them in Windows and how to create your own disk images. Hopefully we have managed to answer all your questions on this subject. If we didn't, let us know in the comments form below. We will do our best to help.

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