We will download the latest image for Ubuntu Server (version 14.04.3 LTS as of this writing) and write it to a usb flash drive. This will be used to install Ubuntu Server on a brand new OS free desktop PC.

Ubuntu Server is a ‘headless’ environment. That is, it is not meant to be used with a monitor or graphical user interface, but via a SSH terminal window from a different machine.

You will need an usb drive of at least 2Gb of storage (all the data on it will be deleted).
I’m using a windows 7 professional machine.

Download the .iso image file

Go to www.ubuntu.com and click on Server on the top menu.
Once there click on the “Download Ubuntu Server” button:

Then click on the “Download” button for Ubuntu Server 14.04.3 LTS:

You will be asked to save the image file (ubuntu-14.04.3-server-amd64.iso in my case).
Save it to a known location on your system.

Write the image onto the usb flash drive (from Windows)

I’m using Win32DiskImager for this. Please download and install it.

The image writing process will override the entire usb flash drive anyway, deleting all your data, so you don’t really need to format it beforehand.
Insert your usb flash drive on the computer and note which drive letter windows assigned to it, it is drive d: in my case.

Now run Win32DiskImager, you will be presented with this interface:
Be sure to select the correct drive letter under “Device” or you will potentially destroy an external hard disk, flash drive or sd card!
In my case I only have one drive plugged in so it correctly gets recognised as drive d:

Now click on the browse icon to locate the image file we downloaded above.
Make sure you change the filter from *.IMG to *.* or you won’t be able to find the .iso image file:

Now click on “Write” to begin writing the image to the usb flash drive:

That’s it, safely eject your newly created Ubuntu Server usb flash drive and it’s ready to go!