I was planning to install Windows 8 Developer Preview on my netbook so I downloaded Microsoft Windows 7 USB/DVD Download Tool. Windows 7 USB/DVD Download Tool by Microsoft allows you to create bootable USB flash drive for Windows 7 and Windows 8 Developer Preview. This is specially useful for installing Windows operating system on netbooks or computers without optical disc drive.
While it starts to creating bootable USB device, it stopped and shows an error message "We were unable to copy your files. Please check your USB device and the selected ISO file and try again."
Well, don't fret. Neither your USB thumb drive spoiled nor ISO file causing the error. I've found a guide to fix this. UPDATE: Disable Antivirus first. Open command prompt with admin rights and run the diskpart tool:
select disk # (# is the number of your USB. Make sure you selected the correct drive)
create partition primary
select partition 1
format quick fs=fat32
When you done, Windows 7 USB/DVD Download Tool should be able to copy files to your USB thumb drive.