To create a bootable, external USB device (hard drive or thumb drive) consider the following steps … WARNING: It is possible to format ANY drive with this process so be absolutely sure you target the correct drive!

C:\> diskpart

Microsoft DiskPart version 6.1.7600
Copyright (C) 1999-2008 Microsoft Corporation.
On computer: LAB-WIN7-DEV

DISKPART> list disk

Disk ### Status Size Free Dyn Gpt
——– ————- ——- ——- — —
Disk 0 Online 149 GB 0 B
Disk 1 Online 1928 MB 0 B

DISKPART> sel disk 1

Disk 1 is now the selected disk.

DISKPART> clean

DiskPart succeeded in cleaning the disk.

DISKPART> create parti prim

DiskPart succeeded in creating the specified partition.

DISKPART> active

DiskPart marked the current partition as active.

DISKPART> format fs=NTFS quick

100 percent completed

DiskPart successfully formatted the volume.

DISKPART> assign

DiskPart successfully assigned the drive letter or mount point.

DISKPART> exit

Leaving DiskPart…

Once the disk is formatted you have to install a windows operating system on it for it to actually be bootable. Most often I am creating such external bootable media so that I can “image” the computers I boot. In this case a full blown version of Windows is unnecessary. Instead, I create a “windows pre-install” boot environment using Microsoft’s Windows Automated Installation Kit or WAIK for short.