Mount disk images as writable disks with OSFMount


OSFMount from Passmark Software is a free disk image mounting software with some nice features that distinguish it from similar programs; specifically, OSFMount can mount image files as WRITABLE disks, and also allows to create virtual drives in memory.

Mounting means using a file as a virtual disk in My Computer. There are several utilities that can write the whole contents of a CD, DVD or hard disk to create a disk image file (with file extension ISO, IMG, NRG, DD etc). With disk mounting software like OSFMount You can then assign the image file to a drive letter and use it as a virtual disk drive.

This is useful in many instances; for example is netbooks without an optical drive, where you can download the image of an original installation CD/DVD, mount the image and install the program from the mounted image. Another example is creating backup images of Your hard-disk and with the help of disk mounting software You can access single files from the image without the need to restore the whole disk.

Reading vs. Writing: many disk mounting software can only create read-only disks but OSFMount allows creation of writable drives. This means You can take an image file, make it appear as a drive, change the files and folders inside and then save the modified image file.

RAM drives: another useful feature of OSFMount is creating drives in memory (RAM drives). If you have lot of memory there are benefits to be had to making a very fast virtual drive in memory, which can speed up working with applications considerably. An example would be creating a RAM drive for Photoshop temporary files.

Typically all the contents of a RAM drive are lost after shutting down the computer but OSFMount allows for writing e the contents of the RAM drive to a disk image file for mounting next time You need the files.

Note that after creating a new empty RAM drive you have to format it to desired file system (e g NTFS); if you want to keep the contents of the drive you need to select ‘Save to image file’.

OSFmount screen2OSFmount screen1

On exiting OSFMount the virtual drives remain available as they are created uses Windows virtual disk drivers. For dismounting the drives you can run OSFMount again and save/dismount the drives.


  • Most disk images can be mounted as writable.
  • Supports a wide range of disk image files (IMG, DD, ISO, Nero NRG, WMWare VMDK etc); many of which it can mount as writable. The following are NOT writeable: ISO, BIN, and VMWare Image (VMDK).
  • Create virtual disks in RAM and write the contents to image file afterwards.


  • No windows integration: i.e. no entries in the context menu when right-clicking on an image file, unlike many of the other programs in it’s category.
  • OSFMount virtual CD/DVD is not sufficient for some games that require installation media (use Virtual Clonedrive, Daemon Tools etc instead because they use different virtual disk drivers).

The verdict: a great program if you want to work with your images as writable disks, or if you need to work with RAM images, or if you simply want a reliable image mounting software with some very interesting functionality (note that it will not mount ISO, BIN, and VMWare VMDK image format as writable but will mount IMG, DD, and a host of others as such).

It’s only real drawback it the lack of right click integration in Windows explorer, which is not an insignificant disadvantage in terms of the user experience.

For other, similar programs previously mentioned on Freewaregenius: WinCDEmu, MagicDisk, Pismo file mount

Compatibility: Windows XP, Vista & Win 7, Windows Server 2000, 2003, 2008. Both 32bit and 64bit versions available.

OSFMount is available in the OSFMount homepage.

  • Peter

    If you check the chart on the home page for this utility you’ll note that it doesn’t allow writing to a CD .iso or .bin image. I hope I’m wrong because this could be a useful tool otherwise.

    • Priit

      Yes, Peter, unfortunately this is true. It seems that whatever virtual drive is created with CD/DVD type it will be read-only.

  • Someone

    So, what does it do that PowerISO doesn’t do? – I can edit ISOs with PowerISO, so why would I switch?


  • ruudboek

    Does anyone know if there are any plans to support writing to ISO cd/dvd images?
    Because that would make this the first useful freeware ISO editor.
    People have been waiting for ages for that:

  • Priit

    @Someone: The free OSFMount utility is not meant for authoring CD/DVD images. No need to switch if You already have PowerISO.

  • Priit

    @ruudboek: Do You need to change the images of installation media? Many years ago I was also looking for the same functionality to add some extra software to Windows installation CD. But now I use USB drives, actually a USB microSD adapter with several microSD cards with different Windows installation files, Linux and harddisk utilities. Works OK with exception of some older BIOSes.

  • bartman2589

    You might want to check out ImDisk (, it offers almost identical functionality PLUS context menu entries to help manage mounting/unmounting disk images. As a matter of fact it’s so similar that I have to wonder if Passmark software didn’t maybe swipe some of the code for their product from ImDisk (which I have been using for about 4 years now).

    • Samer

      @ Bartman: thanks for the tip. Looking into Imdisk

  • bartman2589

    Another similar utility that is geared towards working with floppy disk images can be found here: (handy if say you use Dosbox or a Virtual Machine program like VirtualBox/VMWare Player/Microsoft Virtual PC to run older operating systems in a virtual environment but your host system doesn’t actually have a Floppy drive, or your Virtual system expects the data to be on a drive type that’s not really very common, like say a 2.88mb floppy, or 1.67mb floppy (special format developed by Microsoft for software distribution, readable by common 1.44mb 3-1/2 drives), or even a 1.2mb 5-1/4 inch floppy, or a number of other formats even). Can also be used to replace much of the functionality of the shareware program WinImage by allowing you to make disk images of your existing physical floppy disks easily (assuming you have a floppy drive installed that can read the disks in the first place). I haven’t tried using it yet on Windows 7 (I’m on 64 bit and the site claims it’s only for 32bit operating systems), might work in Virtual XP mode though (like I said I haven’t tried yet though), since Virtual XP mode is a virtual machine running 32 bit Windows XP under Virtual PC.