So how do you accommodate the first law of law office computing? This states that it does not matter when you buy a computer, because the price will almost immediately be slashed, leaving you kicking yourself for being impetuous and not waiting a little longer before you rushed out to buy it.

Although there is some seasonal variation in price - high street computer stores will often run special offers during certain times of the year when trade is traditionally slack; the early new year and the summer months for example - the basic fact of life is that when it comes to their cost, computers are unlike almost any other type of office equipment, because after a few years they are almost totally valueless.

For example, many of you will still work in offices where there are typewriters lurking in cupboards that your firm purchased back in the 1960s and which will still work today as well as they did when they were new.

Computers are not like that, because the steady evolution of information technology means your PC will inevitably become obsolete, in the context of being unable to run the latest versions of operating systems and software applications.

Furthermore, unlike typewriters that could always have worn parts renewed, the economics of the PC industry means that eventually you reach a point where it is cheaper to buy a brand-new replacement PC than it is to upgrade an old one.

As for your old PCs? Be reconciled to taking them to the tip, as you will probably find you cannot give them away.

Fortunately, it is possible to maximise the life expectancy of any new PC you purchase by buying the latest, most state-of-the-art system you can afford.

This way - and I appreciate it may sound like standing commercial prudence on its head - if your entry point is this year's technology, then even with the inevitable upgrades to operating systems and the launch of tomorrow's versions of the software programs you run, you can still realistically expect to be using that same machine in six, seven or even eight years' time.

On the other hand, if you try to save money today by purchasing a lower-specification PC containing, in effect, yesterday's technology, that is a false economy because it will become obsolete sooner and need replacing earlier.

Charles Christian is an independent adviser to the Law Society's Software Solutions guide