Download windows 7 usb/dvd download tool
Select your windows 7 iso file ( if you don’t have it as an iso file but just on dvd media you can use a 3rd party piece of software to create your iso from the dvd disk, Such as Poweriso, Ultraiso and possibly other freeware software that can create iso’s too
Note some self-created iso’s (or downloaded) can flag up errors that the format is not right. Even though when burnt to dvd windows 7 installs fine. If it is a working iso ie you have tested it on dvd media. Use this tool to fix your iso file isoavdpcopy.exe
extract exe into same directory as windows 7 iso
run this tool from the command prompt
enter isoavdpcopy followed by your iso file and hit enter
You will get this message if successful
Now reselect your fixed iso with win7 usb tool
Then follow the next few steps to finish process. Select usb and direct installation to your usb drive (drive size required is 4gb recommended)