Install Windows 7 from a USB drive the very easy way
Open the command prompt with admin rights. Type cmd in Start menu search box and hit Shift+Ctrl+Enter.
To keep things really easy, if you see text in upper case, it means this is what you type into the command prompt (you don’t need to type in upper case).
this loads the diskpart application we need to proceed
the image above shows our 4 GB USB drive is listed as DISK 2
so you have to type
SELECT DISK 2 (your USB Drive may have a different number, don’t follow exactly this text it depends on your usb drive)
You will get a successful response “Disk 2 is now the selected disk”
Next we want to clean the USB drive
you will get a successful response ‘DiskPart succeeded in cleaning the disk”.