This post explains why the Windows 7 USB/DVD Download Tool (WUDT) is unable to copy the install files to the USB drive in some cases. The tool allows you to create a copy of your Windows 7 ISO file on a USB flash drive.
Update: If you have problems Windows 7 USB/DVD Download Tool you can try the free alternative Rufus.
You might have heard of the stir that Microsoft’s Windows 7 USB/DVD Download Tool (WUDT) caused last year when some Open Source watchmen recognized that the tool contained code that violated the GPL. Microsoft was then “forced” to release WUDT under GPLv2. Considering the upset in the media about this incident, I expected a luxurious tool that comes with lots of customization features. I was somewhat disappointed to discover it does nothing else but copy the contents of a Windows 7 install DVD to a USB stick and make it bootable.
The funny thing is that WUDT even failed to perform this simple task with my no-name USB stick. This message was the only thing that the Open Source tool could do for me:
We were unable to copy your files. Please check your USB device and the selected ISO file and try again.
At least, my cheap stick wasn’t the cause because everything worked perfectly when I manually did the job (hopefully without violating any Open Source laws). So, I thought, I would write this post for those who might run into the same problems and think they need to buy another USB stick. After all, this is Microsoft software and there are not many options to integrate bugs in such a simple tool.
Anyway, here is what you have to do. Launch a command prompt with admin rights and run the diskpart tool. Note: Before you run these commands read the warning below!
select disk #
create partition primary
select partition 1
format quick fs=fat32
The “list disk” command will show you the connected drives and with “select disk”, you can choose your USB stick.
WARNING: Be careful to select the right drive or else your day won’t have a happy end because if you select the wrong drive you will lose all your data on this drive!
The crucial step here is the “clean” command. It overwrites the MBR and the partition table (thereby, deleting everything on the stick). My guess is that WUDT misses this step and only formats the flash drive. It appears my memory stick had some odd partitions (which is not uncommon). When I tried WUDT again with this prepared stick, the Open Source tool mastered its task without further murmur.
By the way, this is also the reason why you shouldn’t use the Windows Disk Management applet to prepare the USB stick. This GUI doesn’t offer a clean command.
After you prepare the stick, you have to copy the contents of your Windows 7 DVD to the thumb drive, and you are done. If you only have an ISO file, you can use Virtual CloneDrive to mount the Windows 7 install DVD first.
Instead of formatting the partition with FAT32, you can also use NTFS (like WUDT does), but then you need an extra step to make the drive bootable:
Bootsect.exe /nt60 X:
“X:” is the drive letter of your USB stick. Bootsect.exe can be found on the Windows 7 DVD in the boot folder. However, I can’t really recommend using NTFS. My USB stick, at least, appeared to be slower with NTFS.