I thought I should chime in here and hopefully save some people a headache or two.
If you are getting the "Invalid ISO" error, click on the "Home" tab above and read the very first line of text on the page:
The Windows USB/DVD Download tool allows you to create a copy of your Windows 7/8 ISO file
on a USB flash drive or a DVD.
In other words, this tool was designed to work with .iso files containing Windows 7 or Windows 8 setup files ONLY. Trying to burn any other kind of .iso file will most likely
If you need to burn some other kind of .iso file to a CD/DVD
, Windows 7/8/10 offers this feature natively, just right click on the .iso file and select "Burn disc image".
If you need to burn some other kind of .iso file to a USB drive
, there are other tools that will do exactly this:
ISO to USB
Hope this helps someone.