Install Windows 7 from a USB drive

There comes a point in your life, where do you don't stock up on blank DVD's or CD's, and all you have are external hard disks and flash drives. Now, what happens when you need to re-install Windows and you have no proper disc to do it with? Perhaps the original disc is damaged (but can be recovered), or you only have the ISO version (which is completely legal, so long as you plan to register it with a valid key) of it?

This happened to me recently, and I managed to figure out how to do it. Its possible to install Windows 7 (or Windows 8, if you want to) from a USB drive, be it an external hard disk or a small flash disk. This post is about how its done.

You'll need:

• Another PC with Windows on it (at least XP), or if you haven't re-installed on the current PC, don't (at least not yet). You'll need it.
• An external hard drive, or a flash disk. They must have at least 4GB of capacity IN TOTAL.
• Your Windows 7 (or Windows 8) disc or ISO (must be mounted).

Now on to the juicy parts:

PART 1

Fig. 1

Fig. 2

1. Plug in your flash disk or hard drive into a USB port of the computer with Windows on it, and back up all of the data into a safe place, because we need to erase and format it.
2. Open the command prompt with administrator rights. You can do this by navigating to C:\Windows\System32, right clicking on cmd.exe, and then clicking on Run as Administrator. Note that if you don't have Windows installed to drive C:/ you will have to navigate to the drive its installed on. Alternatively, you can go to your Start Menu, click on All Programs, then Accessories, and then right click on Command Prompt and select Run as Administrator.
3. Once the command prompt is open, type DISKPART and press enter. Refer to Fig. 1. 
4. Type LIST DISK and press enter. Remember the disk number of the drive you plan to boot from. The size and free space of the disk will give you a clue as to what is what.
5. Now you need to type the following commands IN ORDER,  like you did for the ones above. 

• SELECT DISK ### (where ### is the disk number you noted earlier)
• CLEAN
• CREATE PARTITION PRIMARY
• SELECT PARTITION 1
• ACTIVE
• FORMAT FS=NTFS (Note that if you are working in XP, this command won't work. You need to navigate to the drive in my computer, right click on it, and click on format. In the new window, make sure you format to NTFS and not FAT32 or exFAT)
• ASSIGN
• EXIT

PART 2

1. Keep the command prompt open.
2. Insert your Windows disc into your DVD drive or mount the image. Make a note of the drive letter of your Windows disc, as well as the drive letter of the drive you want to boot from.
3. Go back to the command prompt and type #: CD BOOT (where # is the drive letter of your Windows disc) and press enter.
4. Type BOOTSECT.EXE /NT60 #: (where # is the drive letter of the disk you want to boot from) and press enter. This fancy pants command makes the drive boot-able. Almost there!
5. Copy the contents of the Windows disc onto the empty boot-able drive. Once that is done, your device is ready to be booted from, and installed.
6. Now this step is hardware specific, and I cannot help you during this because there are literally hundreds of motherboards out there. You need to make sure that your computer can boot from a USB device, and there is usually a setting for this in your BIOS. Refer to your motherboard manual for this. If you don't want to do this, you can always risk it and hope that your computer is already configured to boot from USB.
7. Proceed to install Windows as you normally would. \:D/

I hope this helped you in some way. Enjoy!