Teach you Installing Windows 7 From USB Drive 3 Steps Easy Process
There are guides on how to prepare your USB drive so you can put all the Windows 7 files on it, then boot from your USB drive and install Windows 7, but they are all lengthy and require a bunch of commands.
The Easy Process of Installing Windows 7 From USB Drive:
Note: Make sure your motherboard is capable of booting off a USB drive or this will not work. Also, backup any files on your USB drive because it will be formatted.