It is simple to install Windows 7 or Vista from any USB media as long as you follow this guide. First you need to fulfill the following list of prerequisites, which I have expanded on much more than most guides similar to this one, so that you will be prepared for everything:

• A USB stick or similar USB storage device (aka” USB Flash Drive”) with a minimum of 3 GB capacity
  (Tip: Some USB drives don’t work well as boot devices on certain systems. If you have issues, try a different flash drive.)
• Windows 7 (or Vista) source files (from ISO or DVD)
  (Tip: If you have obtained an ISO file, you may extract it using WinRAR.)
• BIOS Settings and Hardware Checks:
  1. Change the boot priority of USB devices so that they are above any harddisks.
  2. Check the boot order for your hard disks. If your USB connected device shows up here, usually you need to hit “Page Up” (PGUP) to move it all the way to the top.
• Check that your computer supports booting from USB devices. If not, then you probably can’t boot from your USB media. You would need to run the installation from your DVD-drive or obtain an external DVD-drive or adapter.

(Tip: See your PC manual or a tech savvy friend if you have issues with this step. Normally you need to press either F2, F3, F5 or F12 to access the boot menu. Sometimes it helps to press ESC to see what you need to press if neither of those are working.)

Now let’s make a bootable USB device!

But first…

• You need to obtain the correct version of BOOTSECT.EXE (64-bit/x64 or 32-bit/x86)
  If you’re making the USB bootable media for a 64-bit version of Windows on a 32-bit version of Windows, you need to get yourself the 32-bit version of the BOOTSECT.EXE tool used in this guide, as the 64-bit version found included in the 64-bit source files won’t run on a 32-bit OS. You should be able to get this from any 32-bit install source for Windows 7 or Vista. I cannot put it on my blog, because it is prohibited by the Microsoft EULA.

1. Plug in your USB stick and backup any important files that you may want to keep.
2. Open Command Prompt with administrator rights using either of the following methods:
   • Hit the Windows key + R and type CMD. Hit CTRL + SHIFT + ENTER.
   • Type CMD in the Start menu search box. Hit CTRL  + SHIFT + ENTER.
   • Go to Start > All programs > Accessories and right-click on Command Prompt, then select “Run as administrator“.
3. Type the following commands in the Command Prompt box to find the disk number of your flash disk:
   • DISKPART
   • LIST DISK
4. Identify your flash disk and note the disk number, then enter the following commands – assuming your USB stick’s disk number is 1:
   • SELECT DISK 1
   • CLEAN
   • CREATE PARTITION PRIMARY
   • SELECT PARTITION 1
   • ACTIVE
   • FORMAT FS=NTFS QUICK
     (QUICK is the switch for Quick Format. Run the command without QUICK if you want all sectors checked. This could take a long time depending on the size and speed of the disk.)
   • ASSIGN
   • EXIT
     (BUT DON’T CLOSE THE COMMAND PROMPT YET!)
5. Still in Command Prompt? Good, because  you’ll need it again in a few seconds…
6. If you have an ISO image of Windows 7 or Vista, you may now extract it if you haven’t already, then follow step 6.1. If you have a DVD, follow step 6.2:
   6.1: Assuming you extracted the ISO to C:\Win7, bring up your Command Prompt again, then browse to the BOOT folder by typing: “CD C:\Win7\boot”
   6.2: Assuming your DVD drive letter is “D”, bring up Command Prompt and browse to the BOOT folder by typing “D:CD boot”.
7. Assuming your USB stick drive letter is “E”, type the following command to make the USB stick bootable:
   • BOOTSECT.EXE /NT60 E:
8. You should see a message saying “Successfully updated NTFS filesystem bootcode. Bootcode was successfully updated on all targeted volumes.”
   
   If you get an error about x64/x86 incompatibility at this stage, you need to obtain the correct version of BOOTSECT.EXE – see the 4th bulletin at the very top of this guide for more info.
9. Copy all of your Windows 7 / Vista contents to the USB stick.
10. Your USB stick is now ready for use! Remember to enable USB boot and change boot priority so that USB-drives are above any harddisks in the boot priority in the BIOS. Refer to your system manual for instructions on how to do this. Also, remember that some USB sticks don’t work as well as others as boot devices, especially with certain older systems that claim to have USB boot capabilities. I can confirm that it worked with a SONY 4GB USB stick on a Dell Latitude E4200 for me, and has worked with many others for people I know. The least reliable kind of USB stick seems to be the variety that come as USB adapters for different memory cards, like SD Card or Memory Stick, BUT they may work even if they don’t appear as USB devices, as they will often simply be listed as harddisks instead.