Let’s say you have downloaded Windows Vista OEM from the Internet and you want to install it on your PC. The problem is, you don’t have blank DVDs, or you don’t have access to your optical drive. However, you have a USB memory stick with enough capacity. You can copy the downloaded files to the memory stick, boot from the USB instead of CD/DVD and simply run the setup from there, right? Not quite. I tried to do this and quickly discovered that it’s not that easy.

First, you need to prepare your USB drive so it works like a bootable CD or DVD. To do this, you have to have a functioning Vista or 7 system, so you can run a few commands.

1. Plug in your USB stick (I suggest 4GB) and format it (right click/format) – this will erase everything from this drive.
2. Open the command prompt as administrator (click on Start, then All Programs, click on Accessories, then right click on Command Prompt and select Run as Administrator)
3. Type diskpart and press Enter
4. Type list disk and press Enter – this will show all available drives connected. Disk 0 will be the primary hard drive. Disk 1 should be the USB flash drive, unless you have other hard drives in your PC. The flash drive should have the highest number because you added it last. For this exercise, we’ll treat your USB drive as disk 1.
5. Type each of the following commands one by one and press Enter. Successful operation should be confirmed every time by the command prompt:
6. select disk 1
7. clean
8. create partition primary
9. select partition 1
10. active
11. format fs=fat32
12. assign
13. exit
14. Go to Windows Explorer and find the Windows 7/Vista installation files you downloaded earlier
15. Copy the contents to your USB flash drive

Your USB drive is now ready. All you need to do now is restart the PC, plug in your USB drive and let the setup run. If it doesn’t work, then you’ll have to adjust the settings in BIOS, so that the first boot device is the USB drive.

To access BIOS, restart the system again and press DEL (in most systems) or F2 (in many others) or consult your PC manual. Once there, find boot priority or boot order and select the USB device as first boot device.

I found these instructions at the DotNetWizard Web site. However, on Kevin’s Blog, there is another method. Kevin’s method uses the NTFS file system for formatting and is slightly longer than this one, as it includes some extra steps to make the USB bootable.