Kids' stuff
I have had a brilliant idea for a computer game, but haven't a clue where to start. Could you recommend a good book/website/ CD-Rom that could help me? Christopher Keenlyside (aged 10)

Jack Schofield replies: Most commercial games are produced by large teams with the help of graphics and music specialists, but it is still possible for individuals to write enjoyable and hugely successful games. Examples include Tetris, FreeCell and Snake. Also, games designed for educational purposes, or to run on the web or on mobile phones, can be much smaller and simpler than the latest movie-based blockbuster.

There are lots of tools that make it easier to write games, especially adventure games. Most run on Windows. See Engines/Authorware for Non-Programmers for a list. Alternatively, try Squeak, which is a very accessible version of the Smalltalk object-oriented language. Squeak not only knocks most computer languages into a cocked hat, it is easy to use and educational. It also has some games that could help you get started.

For background reading, GamaSutrawill teach you a lot about how games are developed, and how the industry works. You could also read Chris Crawford's The Art of Computer Game Design (1982), which is available free online.

Housekeeping
I have been told that dust building up inside my computer can cause it to heat up and become unstable. However, I have also been told that vacuum cleaners generate static electricity that can damage sensitive electronic components. What is the best way to clean the dust from inside my machine? John English

JS: All of that is true, though I would not expect dust to be a major problem with PCs in most inhabitable environments. The main thing is to make sure the fans do not become clogged up. There are "approved PC vacuum cleaners" such as the DataVac P, though I've got away with using a long extension tube on an ordinary domestic machine. The standard recommendation is to blow dust away using a can of compressed air, but avoid blowing compressed air into disk drives.

Fan noise
My PC has developed an alarming hum/buzz, which I assume must be the fan. Can I expose the fan and lubricate it? And if so with what: oil, graphite? S Lord

JS: If a fan is kept clean, I would expect it to outlast the useful life of the PC. If it starts making a noise, my preference would be to replace it, especially if you have an AMD processor rather than an Intel Pentium 4. (When overheating, the P4 turns itself off to avoid meltdown.) However, the Fan maintenance web page provides a good illustrated guide to oiling a fan with sewing machine oil. See www.dansdata.com at your own risk!

Degauss
There's a button on my monitor called degauss, which makes a noise when I press it. What does it do to the monitor? David Boards

JS: Degauss is derived from Johann Gauss, who studied the effects of electromagnetic fields. Degaussing is a common way of erasing magnetic media such as floppy and hard disks. It is used in monitors because a colour cathode ray tube has a screen shadow mask or aperture grill just behind the screen. If the shadow mask is affected by the earth's natural magnetism or other magnets, electrons will not be directed to the right spots of phosphor on the screen and the image will be imperfect. Pressing the degauss button remagnetises the shadow mask to compensate for the effects of the earth's magnetic field. Most monitors automatically degauss when you turn them on, so the degauss button is rarely needed, unless you have a monitor that swivels through 90 degrees, or you move the monitor somewhere where the earth's magnetic field is different, eg Australia.

Backchat

· Carole Watts asked about pop-up adverts that were appearing from a Windows Messenger service in Windows XP, and I explained how to block them. Pete Baker complains, very reasonably, that I "failed to identify that this is merely the symptom of a potential more dangerous problem (at least in security terms). The preferred solution should always be for the user to either install or properly enable a firewall." See www.microsoft.com/windowsxp and Microsoft Knowledge Base article 330904, Messenger Service Window That Contains an Internet Advertisement Appears.

· Last week, I said "hard drive space now costs about £2 per gigabyte". Smiling Crow (sic) points out that prices have come down since I last bought one. An 80GB drive now costs about 75p to £1 per megabyte.