While Paul Thurrott was playing with the official Windows 7 USB/DVD Download Tool, creating a bootable USB stick for his netbook upgrade, he ran into an interesting snag with certain discs. The tool, when directed to use an ISO dumped via ImgBurn, would error out. Everything was to UDF spec, so what was going on here?
I’m not a UDF expert, hell not even a novice, but I skimmed through ECMA-167 and the reflected tool code. It appears there are two (possibly more) “navigation buoys” within UDF-formatted ISOs that point to important chunks of the image called Anchor Volume Descriptor Pointers (AVDPs). The first AVDP is somewhere near the top of the image. The last AVDP is located in what appears to be the last logical block of the image. (My guess is this is to support bi-directional reading.)
So assuming each logical block of the image is 2048 bytes large, one could also assume the last logical block is –2048 from the end of the file, right? Well, that’s what the tool assumes. It checks for the last AVDP at the start of the last logical block, doesn’t find it, and bombs out.
I haven’t read through the entire spec., but I doubt there’s anything in here regarding the container of the UDF formatted data.
While one could argue Microsoft Store-downloaded ISOs are comprised in a compatible manner and therefore this scenario is unsupported it wouldn’t have been hard to add some AVDP seeking code.
As a quick hack to resolve this issue, I wrote a tool that merely finds the AVDP in your ISO file and copies it to offset (EOF-2048). This will allow you to use your own ISOs with the Microsoft tool. Microsoft.NET 2.x or higher required.

Pingback: Windows 7 USB/DVD Download Tool Creates Bootable USB Flash Drive - The Winhelponline Blog
Pingback: Nerd Alert | Gecko Bloggle
Pingback: Code in Windows 7 USB/DVD Download Tool Violates Open Source License | Windows 7 hacker
Pingback: Pasang Windows 7 Guna USB Drive. « Masalah Komputer
Pingback: Lidenskap: Teknologi » Windows 7: 30 tips og hvordan installere fra minnepenn
Pingback: Windows 7 USB DVD download tool: “not a valid iso” | Windows 7 Themes
Pingback: MTPH Software: Blog : Microsoft ends GPL saga; WUDT source code released :
Pingback: Download of the Week: Windows 7 USB/DVD Download Tool « Techknology's Blog
Pingback: MikHo Software » Blog Archive » Creating Bootable Vista / Windows 7 USB Flash Drive
Pingback: Windows 7 vom USB-Stick installieren « dotTux
Pingback: Microsoft ends GPL saga; WUDT source code released | PIRZADEH.se | Nima Pirzadeh
Pingback: Windows 7 Ultimate para tu Netbook | DESCARGAR PROGRAMAS GRATIS
Pingback: Problem with Windows 7 USB / DVD tool (Error : Not a valid ISO file) | Choto Cheeta Online
Pingback: usb 启动盘制作的几种办法
Pingback: Neuinstallation ohne DVD-Laufwerk
Pingback: Windows 7 en USB | MonedaVirtual
Pingback: Solución: Windows 7 USB/DVD Download Tool Invalid ISO file | Windows 7k: Lo que Necesitas para Windows Seven
Pingback: ThinkPads and SSDs Part 1: Preparation « Matthew Ammann
Pingback: Windows 7 USB DVD Download Tool | Rich's Blog