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A step-by-step guide to creating a flash drive version of Windows

Creating a bootable flash drive version of Windows Vista or Windows 7 isn't as complicated as you may think. This step-by-step guide shows you the way.

My laptop's DVD-ROM drive recently gave up. Discs wouldn't read or even spin up from it, and its laser kept making a wheen-wheen noise whenever the computer booted. I attached an internal DVD-ROM drive by way of a USB-to-SATA bridge. That worked for a while – but then it too quit.

This was aggravating because, after several software installs and changes to the system, I needed to mop down the computer and reinstall Windows 7. Without an optical drive, this would be a chore, so instead I created a bootable flash drive version of the Windows 7 installation media.

The process isn't as tough as it may seem. To get started, you need the following items:

  • A flash drive of at least 4 GB.
  • A running installation of Windows 7 to which you have administrator access.
  • A copy of the Windows 7 installation media.
  • If your copy of Windows 7's install media is in the form of an .ISO file, you'll need a copy of the free, open source 7-ZIP archive utility.

That's it --now just follow these steps to create the flash drive:

  1. Go to an available Windows 7 system.
  2. Mount the flash drive, and make sure Windows recognizes it as a device. If this is the first time you've used the drive in that particular installation of Windows, it may take a moment to be recognized.
  3. Open an elevated command prompt, and type diskpart to launch the DISKPART utility. This is the command-line, disk-partitioning tool created to replace fdisk from previous versions of Windows (and DOS before it).
  4. In diskpart, type list disk to obtain a numbered list of all the currently mounted disks in the system. The flash drive you plugged in will not have any special identifiers other than its size, so pay close attention. (It typically registers as the last drive in the list, but that's not a universal rule.)
  5. Type select disk # -- with # as the number of the flash drive. For example, if your flash drive showed up as Disk 4, you'd type select Disk 4.
  6. Type clean to remove any existing partition information from the disk. This is important because there may be partition information left over that might prevent the drive from working properly as a boot drive.
  7. Type create partition primary to create a new, primary partition on the disk.
  8. Type active to mark the current partition as bootable. This is extremely important. If the partition isn't marked as bootable, no computer will recognize the drive as a bootable medium in the first place.
  9. Type exit to leave diskpart.
  10. Unmount the drive (right-click in Explorer and select "Eject"), unplug the drive, and then plug it back in. This step is optional, but it seems to help clear the system of any lingering incorrect information about the drive.
  11. Right-click on the drive icon in Explorer and select Format. Use the following options: NTFS for the file system and 4096 bytes as the allocation unit size. Check the "Quick Format" option. If you're not too sure about the quality of the drive, you can uncheck "Quick Format," but the format process will take much longer. A volume label is not required, but it can be useful. (I just use "Win7.")
  12. Click Start to format the drive.
  13. When the format operation is finished, insert your Windows 7 installation media. If you're using an .ISO, use 7-ZIP to open the .ISO as if it were an archive, and copy the contents of the .ISO to a folder.
  14. Copy the entire contents of the installation disk -- exactly as-is -- to the flash drive. This may take several minutes; refresh your coffee in the meantime.
  15. When the copy operation is finished, unmount the drive.

The resulting flash drive should boot on any system. If it doesn't work, the drive you're using may not support booting, or it has been configured to mount as a different kind of storage device than one recognized as a boot device.

Once booted, the installation process should proceed normally. Just make sure not to use the flash drive itself as a target for the install.(From what I've seen, Windows should prevent you from doing this anyway.) One convenient byproduct of having your Windows install media on a flash drive is that you can add other programs to the drive -- like the Malicious Software Removal Tool -- which you can run from the Windows PE (rescue environment). Plus, unlike a custom DVD-R, you can add or remove software from the drive without having to reburn it.

It may also be possible to use this technique on a boot or install processes to stall.

Also note that the exact method by which you enable USB booting varies widely between systems. With some of them, the boot device can be selected by pressing F12 at startup; with others, it needs to be set manually in BIOS beforehand.

Serdar Yegulalp has been writing about personal computing and IT for over 15 years for a variety of publications, including (among others) Windows Magazine, InformationWeek and the TechTarget family of sites.

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