From there, select the IPSW file you want to install to the device.
If an update isn't working properly or i Tunes isn't recognizing the IPSW file that it downloaded, you can delete or remove the file from the above location.
Some file formats use similarly spelled file extensions that can be confusing when you're having trouble opening the file.
There shouldn't be any reason to convert an IPSW file to another format.
The way it exists is necessary for communicating software updates through i Tunes and to Apple devices; converting it would mean losing functionality of the file altogether.
This lets you see the different DMG files that make up the IPSW file, but you can't apply the software update to your Apple device this way — i Tunes still needs to use the IPSW file.
If you find that an application on your PC tries to open the IPSW file but it's the wrong application or if you would rather have another installed program open IPSW files, you can change the default program settings in Windows.
If you do get an earlier version like I had to do on my 64-bit Windows system, don’t bother trying to update it because it’s going to want you to get i Tunes 12.