Originally designed to protect your monitor from damage, today we tend to take the humble screensaver for granted. After all, you don't actually need screensavers these days, do you, what with flat-screen monitors being all the rage?

Well, there was no question that old CRT monitors were prone to suffer from 'burn-in', where a monitor that routinely displayed the same static text or image for prolonged periods could end up with a permanent ghost-like impression 'engraved' on the screen's internal phosphorous coating.

Screensavers were designed to prevent burn-in by displaying a random, ever-changing pattern during periods of inactivity. These days, CRT monitors are far less susceptible to the problem and TFT monitors should be exempt altogether. However, anecdotal evidence suggests that theory doesn't always match reality, and some intensive computer users still report the shadowy signs of burn-in.

The best screen-saving measure of all is turning off your monitor during extended periods of idleness. Automatic shut-downs can be easily configured in the Windows Power Options Properties screen, which is accessible via the Screen Saver tab of Display Properties (right-click on the Windows Desktop and choose Properties from the pop-up menu).

Still, screensavers can serve a purpose, particularly for short breaks when you remain beside your computer. The very best are fascinating, soothing or informative, and if nothing else they help to keep your on-screen content private. If you don't find one that you like, you can always make your own.

AquaReal
Pretty, photo-realistic fish, swimming around in a gorgeous aquarium adorned with coral and offset quite beautifully against a background of gently morphing lighting. You can tickle and feed your fish, swap angelfish for clownfish, and add your own background music to complement the built-in bubble sounds.

AquaReal is similar in concept and execution to the Marine Aquarium screen saver included in the add-on Plus! pack for Windows XP. However, this one can also function as full-motion wallpaper - it uses the Windows Active Desktop feature - and this sets it apart.

A free but basic demo version is available with a handful of fish, but you'll have to shell out to fully stock and fine-tune your virtual aquarium.

The hardware requirements are also pretty demanding - we had to download graphics card updates and the latest version of DirectX to get it working at all - so we'd suggest experimenting with the demo first to find out if your system can cope.

Website: www.digifish.us
Price: Free unlimited demo; $20 (about £11) for the full version

EarthView
Like AquaReal, EarthView works as both a Windows Desktop background and a screensaver. Similarly relaxing, it shows you planet Earth in real time as viewed from 10km out in space, updating frequently to track the movement of sunlight across the globe.

You can choose to view selected towns and cities, with or without local times, and set the level of cloud cover to suit. You can also select between photographic, scientific and artistic impressions of the planet and alternate between flat map and globe views.

In fact, EarthView comes with a bamboozling array of configuration options and it's undoubtedly very clever. Truth to tell, though, once you've watched a full 24-hour progression from day to night and back again, the novelty wears a little thin. The paid-for version of this screensaver buys you greater map detail and the option of downloading real cloud data from the internet.

Website: www.desksoft.com/EarthView.htm
Price: Free 15-day demo; $20 (about £11) to buy

Drawing Hand
If you've ever pondered the mechanics of the artistic process, now's your chance to see it in action. The Drawing Hand screensaver is, er, a hand that draws. Sit back and watch as King, a lion, takes shape on your screen. From the initial outline sketch to the final furry flourish, every brushstroke and charcoal smudge is captured. As a learning process, arguably, or just for curiosity's sake, it's quite entertaining.

However, there's a definite limit to how many times you can bear to see the same maned moggy materialise on your screen, so you'll soon want to download fresh drawings from an online gallery of over 200, ranging from fine art to fast cars. The software will nag you until you buy the full version, which costs about £14. To turn your own drawings into screensavers, try the related program called ArtStudio, available from the same source.

Website: www.drawinghand.com
Price: Free demo; $25 (about £14) to buy

Electric Sheep
More artwork here, but this time it's strictly hands-free. This screensaver "realises the collective dream of sleeping computers from all over the internet", which is a cute way of saying that your computer hooks up to a server and joins a communal number-crunching exercise. It's similar to those distributed-computing models where hundreds or thousands of computers work together to solve problems or analyse data.

Here, though, the output is a sheep, which is to say a fractal flame, which is to say an animated image randomly generated by a lot of very long numbers. View the web gallery to get a flavour of what's in store. Geeky, yes; pretentious, perhaps; but we have to say that some of the creations arriving on our screen were beautiful and mesmerising. An always-on broadband connection is essential.

Website: http://electricsheep.org/index.cgi?&menu=about
Price: Free

The Matrix Screensaver
This is just one of many Matrix screensavers, in fact, but reputedly it's one of the best. It's certainly straightforward, with green computer code that drips down the screen Matrix-style and a good deal of pseudo-scanning. If you tell the software your name in the settings section, it periodically sends you messages: "Wake up Bert ... The Matrix has you ... Follow the White Rabbit ...", and similar referential bunkum.

Without question, this is one for serious fans of the movies but we include it here to illustrate that film-related screensavers are in abundance. In fact, these are often designed by film buffs to prove they can do better than the official screensavers released by the studios, and sometimes they succeed. However, do be wary of spyware and viruses.

Website: www.meticulous-software.co.uk/downloads.htm
Price: Free

Online News
Altogether more useful is Online News, a shareware screensaver that grabs news headlines and displays them in a large, clear font in boxes on your screen. It uses the relatively new and increasingly popular Rich Site Summary technology that enables news providers to feed constantly updating headlines to any compliant application.

Should you notice a headline of interest, you can select it with the keyboard arrow keys and up pops a short summary of the story still within the screensaver. If you want to learn more, press the F5 key and the relevant web page opens in your browser, deactivating the screensaver in the process.

The real attraction is that you can choose your own news sources to suit your interests: news, technology, entertainment, sport or whatever. You do, however, have to be connected to the internet while the screensaver is running. Although it's still in development, we found it immediately addictive.

Website: www.coolscreensavers.com/onlinews.html
Price: Free demo; $15 (about £8) to buy

FireMagic
If, on the other hand, you prefer to switch your brain off while your computer has a break, consider FireMagic or one of many, other similar screensavers. In a nutshell, your screen goes up in synthetic flames, consuming any open windows in the process. Although old-school in design and gimmicky in the extreme, FireMagic is actually rather well done.

It also affords a welcome level of control, including a range of themes, sound effects, different colour palettes, fireworks and fireballs and the option to add your own scrolling, flaming text. Paying the $18 (£10) registration fee gets rid of the omnipresent nag screen that invites you to reach for your credit card.

Website: www.fpsoftlab.com/firemagic.htm
Price: Free demo; $18 (about £10) to buy