Here's quick installation windows 7 from USB
taken from Windows 7 Forums
Note: Back up the files from your USB drive, as it WILL get formatted in this process and all data on it will be lost!
1. Get a USB Drive, it must be at least 4 GB.
2. Plug the drive into your PC.
3. Open a command prompt as administrator. (Right click, Open as Admin, or Ctrl+Shift+Click)
4. Get the drive number by typing:
diskpart
list disk
On my machine the USB disk was number 1.5. Format the drive by typing:
select disk 1
clean
create partition primary
select partition 1
active
format fs=NTFS
assign
exit6. Mount the Windows 7 beta iso or insert the disk.
7. Navigate to the boot directory
cd E:\boot (Where E is the drive letter of the DVD)8. Using bootsect, we’ll make the USB drive a bootable NTFS drive, ready for a Windows 7 image:
bootsect /nt60 F: (Where F is the drive letter of the USB Drive)9. Close the command prompt
10. Copy the installation files from the mounted Windows 7 iso/disk to the USB drive.
11. Reboot the PC, and enter the BIOS (OR you can move to the boot manager menu, usually by pressing F10 if supported)
12. Set the boot priority to boot the USB drive first.
13. Install Windows 7.
