If you see this message, start tapping the key it suggests until a setup screen appears. If you can’t see such a message try pressing the F2, F10 and Delete keys just after the computer restarts. Once you’re in the setup menu, you need to find the options that control the computer’s boot sequence.

This is sometimes called boot device priority or boot options. Change this so that the first boot device is the CD or DVD drive, with the hard disk second, then press the key to save and exit (normally F10). When the computer restarts you should be able to run Linux from the CD.

Once the language select menu appears, choose English, and from the next menu choose ‘Try Ubuntu without making any changes to your computer’. Wait a while and the Ubuntu desktop will appear. Bear in mind that running from the CD this way is slow, so if you choose to install Linux it will be quicker.

Replacing Windows
If you like what you see when you first try Linux then the next step is to install it properly. There are two ways to do this; you can replace Windows, which is a good idea on an old computer, or run the two alongside one another.

First we will explain how to replace Windows, so if you want to use both then skip to the next section.

Before going any further, note that replacing Windows will wipe every single file from your hard disk, so you will need to copy any documents that you want to keep to a CD, DVD or other external disk.

Start the computer with the Ubuntu CD in the drive, choose English, then select ‘Try Ubuntu without making any changes to your computer’. If the display looks garbled, restart the PC and press F4 in the Ubuntu menu. Select Safe graphics mode and press Enter.

Once the Ubuntu desktop appears, double-click on the Install icon on the desktop to launch the install wizard. Leave English as the language and click on Forward. Select London as the location (move the mouse over northern Europe and the map will zoom in). Click on Forward.

The correct keyboard layout should be selected, but otherwise pick English (UK). Select the top option in the prepare disk space window, Guided – Use entire disk, click on Forward and then Continue.

Enter your name and the name you want to log on with, as well as a password. The computer name can be left as it is. Review the options and then click on Install. When it has finished, restart the computer as requested, remembering to remove the CD. Your computer will start up straight into Linux, so move on to the section headed ‘Using Linux’.