Monday 17 June 2019

How to extract the hidden contents in 'special' ISOs and images using 7Zip

7Zip is pretty good at opening ISOs and other files. However, sometimes you may find that it does not expand the contents correctly.

I learned recently of a way to use 7Zip to reveal these 'secret' files.

1. First install 7Zip.

2. Now right-click on the ISO or image file or whatever file you want to extract the contents from.
You will see a context menu.

Normally I click on the top 'Open archive' entry, however if you click on the 'Open archive >' entry, you will then find entries for '*', '#', '#:e', '7z', 'zip', 'cab' and 'rar'.

The 7Zip help menu helps to explain some of these additional options...

The one that is most interesting here is the # option.

This often allows us to open internal images when the normal 'Open' option or double-clicking does not.


Here we have a Lenovo flash update ISO. This contains DOS boot files and a flash utility which when opened up using 7zip or extracted gives an error on the final image when we just use the standard 7Zip 'Open archive' option...

Note the size is 512 bytes!

Note the size is now 31MB!

Error! - it fails to open!

Let's start again...

Right-Click in Explorer on the ISO - Now we use # to open the ISO file...
Next we open the 3.fat entry because it has a large size...

voilĂ ! The boot files are revealed!

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