Download and save the file to your hard-drive by clicking on the link above. Remember where you save it - you'll need to find it in a bit.
Wait for the program to download - it will take about 20 minutes on a dial-up modem. If you are on broadband, it should only take a few seconds.
When it has downloaded, Windows will say 'Download complete'.
Find where you saved it on your computer, double-click the executable file, which you've probably saved as glastonbury_2005_screensaver.exe. The screensaver will then install itself.
The screensaver's controls are accessible through the Screensaver tab of your computer's Display Properties control panel. Find this in the Settings | Control Panels sub menu of your Start Menu, or by right-clicking on your desktop and choosing Properties from the pop-up menu.
Once installed, you can interrupt the screensaver by pressing any key or moving the mouse.