Elevate a command prompt and do the following
- :> diskpart
- :> list disk
- Find the disk ID of the thumb drive (Disk1, Disk2 etc.), this will be X.
- :> select X
- create partition primary
- format fs=ntfs quick
Now take the Win7 install media and extract it locally, there will be a "boot" folder under wherever you extracted it, go back to your elevated command prompt and type: <pathtobootfolder>\bootsect.exe /nt60 $:
$: is the drive letter assigned to your thumbdrive during the preparation stage.
You should now have a bootable, installable, USB thumb drive.