Format the USB

Note: This set of commands assumes that the USB flash drive is addressed as disk 1, you should double check that by doing a list of the disks (type list disk) before cleaning it. If you have multiple hard drives, like an SDFlash drive or a Multibay drive, you could end up wiping your second drive using this command.

diskpart

select disk 1

clean

create partition primary

select partition 1

active

format fs=fat32

assign

exit

Copy Windows Vista/7 DVD ROM content to the USB Flash Drive

xcopy [Device]:\*.* /s/e/f [Flash]:\

Or you can download Windows 7 USB-DVD Download Tool.